| Title: | ODBC Database Access |
|---|---|
| Description: | An ODBC database interface. |
| Authors: | Brian Ripley [aut, cre], Michael Lapsley [aut] (1999 to Oct 2002) |
| Maintainer: | Brian Ripley <[email protected]> |
| License: | GPL-2 | GPL-3 |
| Version: | 1.3-23 |
| Built: | 2024-11-03 06:44:31 UTC |
| Source: | CRAN |
Package RODBC implements ODBC database connectivity.
See the package manual for details of installation and use. (This
will show up as a vignette, and can be accessed via
RShowDoc("RODBC", package="RODBC").)
Two groups of functions are provided. The mainly internal
odbc* commands implement low-level access to the ODBC functions
of similar name. The sql* functions operate at a higher level
to read, save, copy and manipulate data between data frames and SQL
tables. Many connections can be open at once to any combination of
DSN/hosts.
Michael Lapsley and Brian Ripley
R functions which talk directly to the ODBC interface.
odbcTables(channel, catalog = NULL, schema = NULL, tableName = NULL, tableType = NULL, literal = FALSE) odbcQuery(channel, query, rows_at_time = attr(channel, "rows_at_time")) odbcFetchRows(channel, max = 0, buffsize = 1000, nullstring = NA_character_, believeNRows = TRUE) odbcGetErrMsg(channel) odbcClearError(channel)odbcTables(channel, catalog = NULL, schema = NULL, tableName = NULL, tableType = NULL, literal = FALSE) odbcQuery(channel, query, rows_at_time = attr(channel, "rows_at_time")) odbcFetchRows(channel, max = 0, buffsize = 1000, nullstring = NA_character_, believeNRows = TRUE) odbcGetErrMsg(channel) odbcClearError(channel)
channel |
connection handle as returned by
|
catalog, schema, tableName, tableType
|
|
literal |
logical: should arguments be interpreted literally or including wildcards? |
query |
any valid SQL statement. |
rows_at_time |
The number of rows to fetch at a time, between 1
and 1024. Not all drivers work correctly with values > 1: see
|
max |
limit on the number of rows to fetch, with 0 indicating no limit. |
buffsize |
the number of records to be transferred at a time. |
nullstring |
character string to be used when reading
|
believeNRows |
logical. Is the number of rows returned by the ODBC connection believable? |
These are low-level functions called by sqlTables,
sqlQuery, sqlGetResults and similar
high-level functions. They are likely to be confind to the
RODBC namespace in the near future.
odbcTables enquires about the tables on the connected database.
Whether arguments after the first do anything and what they do
depends on the ODBC driver: see the help on sqlTables
for some driver-specific details.
odbcFetchRows returns a data frame of the pending rowset,
limited to max rows if max is greater than 0.
buffsize may be increased from the default of 1000 rows for
increased performance on a large dataset. This only has an effect
when max = 0 and believeNRows = FALSE (either for the
ODBC connection or for this function call), in which case
buffsize is used as the initial allocation length of the R
vectors to hold the results. (Values of less than 100 are increased
to 100.) If the initial size is too small the vector length is
doubled, repeatedly if necessary.
odbcGetErrMsg returns a (possibly zero-length)
character vector of pending messages.
odbcClearError returns nothing, invisibly.
The otheres return 1 on success and -1 on failure,
indicating that a message is waiting to be retrieved
odbcGetErrMsg. odbcFetchRows may return
-2 indicating "No Data", the message that would be
returned by odbcGetErrMsg.
Michael Lapsley and Brian Ripley
sqlQuery, odbcConnect,
odbcGetErrMsg.
Close connections to ODBC databases.
odbcClose(channel) ## S3 method for class 'RODBC' close(con, ...) odbcCloseAll()odbcClose(channel) ## S3 method for class 'RODBC' close(con, ...) odbcCloseAll()
channel, con
|
RODBC connection object as returned by
|
... |
additional arguments passed from the generic. |
odbcClose cleans up and frees resources. It is also the method for the
generic function close.
odbcCloseAll closes all open channels (amongst the first 1000
used in the session).
Channels are closed at the end of an R session, and may also be closed by garbage collection if no object refers to them. In both cases a warning is given (but may not be seen at the end of a console session).
Function odbcClose returns a logical indicating if it
succeeded, invisibly unless a warning is given.
The close method returns 0 (success) or 1, invisibly.
Michael Lapsley and Brian Ripley
Open connections to ODBC databases.
odbcConnect(dsn, uid = "", pwd = "", ...) odbcDriverConnect(connection = "", case, believeNRows = TRUE, colQuote, tabQuote = colQuote, interpretDot = TRUE, DBMSencoding = "", rows_at_time = 100, readOnlyOptimize = FALSE) odbcReConnect(channel, ...)odbcConnect(dsn, uid = "", pwd = "", ...) odbcDriverConnect(connection = "", case, believeNRows = TRUE, colQuote, tabQuote = colQuote, interpretDot = TRUE, DBMSencoding = "", rows_at_time = 100, readOnlyOptimize = FALSE) odbcReConnect(channel, ...)
dsn |
character string. A registered data source name. |
uid, pwd
|
UID and password for authentication (if required). |
connection |
character string. See your ODBC documentation for the format. |
... |
further arguments to be passed to |
case |
Controls case changes for different DBMS engines. See ‘Details’. |
channel |
RODBC connection object returned by |
believeNRows |
logical. Is the number of rows returned by the ODBC connection believable? Not true for some Oracle and Sybase drivers, apparently, nor for Actual Technologies' SQLite driver for Mac OS X. |
colQuote, tabQuote
|
how to quote column (table) names in SQL statements. Can be of length 0 (no quoting), a length–1 character vector giving the quote character to be used at both ends, or a length–2 character vector giving the beginning and ending quotes. ANSI SQL uses double quotes, but the default mode for a MySQL server is to use backticks. The defaults are backtick (‘`’) if the DBMS is identified
as A user reported that the SAS ODBC driver required |
interpretDot |
logical. Should table names of the form
|
DBMSencoding |
character string naming the encoding returned by
the DBMS. The default means the encoding of the locale R is running
under. Values other than the default require |
rows_at_time |
The default number of rows to fetch at a time,
between 1 and 1024. Not all drivers work correctly with values > 1: see
|
readOnlyOptimize |
logical: should the connection be optimized for read-only access? |
odbcConnect establishes a connection to the specified DSN, and
odbcDriverConnect allows a more flexible specification via a
connection string. odbcConnect uses the connection string"DSN=dsn;UID=uid;PWD=pwd",
omitting the last two components if they are empty.
For DBMSs that translate table and column names case must
be set appropriately. Allowable values are "nochange",
"toupper" and "tolower" as well as the names of
databases where the behaviour is known to us (currently
"mysql", which maps to lower case on Windows but not on Linux,
"postgresql" (lower), and "msaccess" (nochange)). If
case is not specified, the default is "nochange" unless
the appropriate value can be figured out from the DBMS name reported
by the ODBC driver. It is likely that "toupper" is desirable
on IBM's DB2, but this is not enforced.
Note that readOnlyOptimize may do nothing, and is not
guaranteed to enforce read-only access. With drivers that support it,
it is used to optimize locking strategies, transaction management and
so on. It does make access to Mimer read-only, and has no effect on
MySQL.
Function odbcReConnect re-connects to a database using the
settings of an existing (and presumably now closed) channel object.
Arguments given in the original call can be overridden as needed.
Note that if a password is supplied (either as a pwd argument
or as part of the DSN) it may be stored in the
connection.string element of the return value, but the value is
(from RODBC 1.3-0) replaced by ******. (This will break
odbcReConnect.)
If it is possible to set the DBMS or ODBC driver to communicate in the character set of the R session then this should be done. For example, MySQL can set the communication character set via SQL, e.g. ‘SET NAMES 'utf8'’.
A non-negative integer which is used as handle if no error occurred,
-1 otherwise. A successful return has class "RODBC", and
attributes including
connection.string |
the full ODBC connection string. |
case |
the value of |
id |
a numeric ID for the channel. |
believeNRows |
the value of |
rows_at_time |
the value of |
Several errors which have been reported as bugs in RODBC 1.3-0
which were in fact ODBC driver errors that can be circumvented by
setting rows_at_time = 1 (and the warning under that argument has
always been there). The drivers involved have been third-party
Oracle drivers and old SQL Server drivers.
Michael Lapsley, Brian Ripley
odbcClose, sqlQuery, odbcGetInfo
## Not run: # MySQL channel <- odbcConnect("test", uid="ripley", pwd="secret") # PostgreSQL: 'case' should be detected automatically channel <- odbcConnect("pg", uid="ripley", pwd="secret", case="postgresql") # re-connection odbcCloseAll() channel <- odbcReConnect(channel) # must re-assign as the data may change ## End(Not run)## Not run: # MySQL channel <- odbcConnect("test", uid="ripley", pwd="secret") # PostgreSQL: 'case' should be detected automatically channel <- odbcConnect("pg", uid="ripley", pwd="secret", case="postgresql") # re-connection odbcCloseAll() channel <- odbcReConnect(channel) # must re-assign as the data may change ## End(Not run)
List known ODBC data sources.
odbcDataSources(type = c("all", "user", "system"))odbcDataSources(type = c("all", "user", "system"))
type |
User DSNs, system DSNs or all? |
A named character vector of DSN descriptions, with names the DSNs.
Brian Ripley
## Not run: > odbcDataSources() test sqlite3 testpg "MySQL" "sqlite3" "PostgreSQL" or testdb3 sqlite3 "MySQL ODBC 3.51 Driver" "SQLite3 ODBC Driver" bdr.xls testacc "Microsoft Excel Driver (*.xls)" "Microsoft Access Driver (*.mdb)" testpg SQLServer "PostgreSQL ANSI" "SQL Native Client" Oracle DB2 "Oracle in OraDb10g_home1" "IBM DB2 ODBC DRIVER - DB2COPY1" testpgw testdb5 "PostgreSQL Unicode" "MySQL ODBC 5.1 Driver" SQLite Datasource SQLite UTF-8 Datasource "SQLite ODBC Driver" "SQLite ODBC (UTF-8) Driver" SQLite3 Datasource mimdb "SQLite3 ODBC Driver" "MIMER" ## End(Not run)## Not run: > odbcDataSources() test sqlite3 testpg "MySQL" "sqlite3" "PostgreSQL" or testdb3 sqlite3 "MySQL ODBC 3.51 Driver" "SQLite3 ODBC Driver" bdr.xls testacc "Microsoft Excel Driver (*.xls)" "Microsoft Access Driver (*.mdb)" testpg SQLServer "PostgreSQL ANSI" "SQL Native Client" Oracle DB2 "Oracle in OraDb10g_home1" "IBM DB2 ODBC DRIVER - DB2COPY1" testpgw testdb5 "PostgreSQL Unicode" "MySQL ODBC 5.1 Driver" SQLite Datasource SQLite UTF-8 Datasource "SQLite ODBC Driver" "SQLite ODBC (UTF-8) Driver" SQLite3 Datasource mimdb "SQLite3 ODBC Driver" "MIMER" ## End(Not run)
Request information on an ODBC connection.
odbcGetInfo(channel)odbcGetInfo(channel)
channel |
connection handle as returned by
|
A named character string giving information on the database and ODBC driver
in use on the connection channel.
Brian Ripley
## Not run: odbcGetInfo(channel) # under Windows XP ## MySQL returned DBMS_Name DBMS_Ver Driver_ODBC_Ver "MySQL" "5.1.35-community" "03.51" Data_Source_Name Driver_Name Driver_Ver "testdb5" "myodbc5.dll" "05.01.0005" ODBC_Ver Server_Name "03.52.0000" "localhost via TCP/IP" ## MS Access returned DBMS_Name DBMS_Ver Driver_ODBC_Ver Data_Source_Name "ACCESS" "04.00.0000" "03.51" "testacc" Driver_Name Driver_Ver ODBC_Ver Server_Name "odbcjt32.dll" "04.00.6305" "03.52.0000" "ACCESS" ## SQL Server 2008 Express returned DBMS_Name DBMS_Ver Driver_ODBC_Ver "Microsoft SQL Server" "10.00.1600" "03.52" Data_Source_Name Driver_Name Driver_Ver "SQLServer" "SQLNCLI.DLL" "09.00.4035" ODBC_Ver Server_Name "03.52.0000" "AUK\\SQLEXPRESS" ## End(Not run)## Not run: odbcGetInfo(channel) # under Windows XP ## MySQL returned DBMS_Name DBMS_Ver Driver_ODBC_Ver "MySQL" "5.1.35-community" "03.51" Data_Source_Name Driver_Name Driver_Ver "testdb5" "myodbc5.dll" "05.01.0005" ODBC_Ver Server_Name "03.52.0000" "localhost via TCP/IP" ## MS Access returned DBMS_Name DBMS_Ver Driver_ODBC_Ver Data_Source_Name "ACCESS" "04.00.0000" "03.51" "testacc" Driver_Name Driver_Ver ODBC_Ver Server_Name "odbcjt32.dll" "04.00.6305" "03.52.0000" "ACCESS" ## SQL Server 2008 Express returned DBMS_Name DBMS_Ver Driver_ODBC_Ver "Microsoft SQL Server" "10.00.1600" "03.52" Data_Source_Name Driver_Name Driver_Ver "SQLServer" "SQLNCLI.DLL" "09.00.4035" ODBC_Ver Server_Name "03.52.0000" "AUK\\SQLEXPRESS" ## End(Not run)
Set ODBC database connection's auto-commit mode.
odbcSetAutoCommit(channel, autoCommit = TRUE) odbcEndTran(channel, commit = TRUE)odbcSetAutoCommit(channel, autoCommit = TRUE) odbcEndTran(channel, commit = TRUE)
channel |
RODBC connection object returned by |
autoCommit |
logical. Set auto-commit on? |
commit |
logical. Commit or rollback pending transaction? |
Auto-commit is a concept supported only by ODBC connections to transactional DBMSs.
If a connection to a transactional DBMS is in auto-commit mode (the
default), then all its SQL statements will be executed and committed
as individual transactions. Otherwise, its SQL statements are grouped
into transactions that are terminated by an execution of commit
or rollback. Switching a connection to auto-commit mode
commits the pending transaction.
By default, new connections are in auto-commit mode. If auto-commit
mode has been disabled, a call to odbcEndTran or an SQL
commit statement must be executed in order to commit changes;
otherwise, pending database changes will not be saved.
odbcSetAutoCommit stops if channel is an invalid
connection. The function returns -1 on error, 0 on
success and on success with a message that would be returned
by odbcGetErrMsg.
Norman Yamada, Yasser El-Zein
Specify or retrieve a mapping of R types to DBMS datatypes.
setSqlTypeInfo(driver, value) getSqlTypeInfo(driver)setSqlTypeInfo(driver, value) getSqlTypeInfo(driver)
driver |
A character string specifying the |
value |
A named list with character values. This should have
names |
This information is used by sqlSave if it creates a
table in the DBMS and is not overridden by arguments typeInfo
or varTypes. Mappings are included for MySQL, PostgreSQL,
SQLite, Oracle, Mimer, DB2 on Windows, and the Microsoft SQL Server,
Access, Excel and Dbase drivers.
The SQL types chosen should be nullable to allow NAs to be
represented. (Bit and boolean types often are not.)
For setSqlTypeInfo none.
For getSqlTypeInfo with an argument, a named list. Without an
argument, a data frame.
Brian Ripley
## Not run: getSqlTypeInfo() getSqlTypeInfo("MySQL") setSqlTypeInfo("Microsoft SQL Server", list(double="float", integer="int", character="varchar(255)", logical="varchar(5)")) ## End(Not run)## Not run: getSqlTypeInfo() getSqlTypeInfo("MySQL") setSqlTypeInfo("Microsoft SQL Server", list(double="float", integer="int", character="varchar(255)", logical="varchar(5)")) ## End(Not run)
Enquire about the column structure of tables on an ODBC database connection.
sqlColumns(channel, sqtable, errors = FALSE, as.is = TRUE, special = FALSE, catalog = NULL, schema = NULL, literal = FALSE) sqlPrimaryKeys(channel, sqtable, errors = FALSE, as.is = TRUE, catalog = NULL, schema = NULL)sqlColumns(channel, sqtable, errors = FALSE, as.is = TRUE, special = FALSE, catalog = NULL, schema = NULL, literal = FALSE) sqlPrimaryKeys(channel, sqtable, errors = FALSE, as.is = TRUE, catalog = NULL, schema = NULL)
channel |
connection object as returned by |
sqtable |
character string: a database table (or view or similar)
name accessible from the connected DSN. If wildcards are allowed
(only for |
errors |
logical: if true halt and display error, else return |
as.is |
see |
special |
logical. If true, return only the column(s) needed to specify a row uniquely. Depending on the database, there might be none. |
catalog, schema
|
|
literal |
logical: wildcards may be interpreted in
|
The argument special = TRUE to sqlColumns returns the
column(s) needed to specify a row uniquely. This is intended to form
the basis of an SQL WHERE clause for update queries (see
sqlUpdate), and what (if anything) it does is
DBMS-specific. On many DBMSs it will return the primary keys if
present: on others it will return a pseudo-column such as ‘ROWID’
(Oracle) or ‘_ROWID_’ (SQLite), either always (Oracle) or if
there is no primary key.
Primary keys are implemented in some DBMSs and drivers. A table can have a single column designated as a primary key or, in some cases, multiple columns. Primary keys should not be nullable (that is, cannot contain missing values). They can be specified as part of a ‘CREATE TABLE’ statement or added by a ‘ALTER TABLE’ statement.
In principle specifying catalog should select an alternative
database in MySQL or an attached database in SQLite, but neither works
with current drivers.
If sqtable contains ‘.’ and neither catalog nor
schema is supplied, an attempt is made to interpret
qualifier.table as table table in
schema qualifier (and for MySQL ‘schema’ means
‘database’, but the current drivers fail to interpret
catalog=, so this does not yet work). (This can be suppressed
by opening the connection with interpretDot = FALSE.) This has
been tested successfully on PostgreSQL, SQL Server, Oracle, DB2 and
Mimer.
Whether wildcards are accepted for sqtable and schema in
sqlColumns(special = FALSE) depends on the driver and may be
changed by the value of literal. For example, the PostgreSQL
driver tested allowed wildcards in schema only if literal
= FALSE and never in sqtable, whereas two MySQL drivers both
failed to match a database when catalog was supplied and always
allowed wildcards in sqtable even if literal = TRUE.
A data frame on success. If no data is returned, either a zero-row data frame or an error. (For example, if there are no primary keys or special column(s) in this table an empty data frame is returned, but if primary keys are not supported by the ODBC driver or DBMS, an error code results.)
The column names are not constant across ODBC versions so the data should be accessed by column number.
For sqlPrimaryKeys and sqlColumns(special=FALSE) the
first four columns give the catalog, schema, table and column names
(where applicable). For sqlPrimaryKeys the next two columns
are the column sequence number (starting with 1) and name of the
primary key: drivers can define further columns. For
sqlColumns(special=FALSE) there are 18 columnns: see
https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqlcolumns-function?view=sql-server-ver15.
Those beyond the first 6 shown in the examples give the
‘ordinal position’ (column 17) and further characteristics of the
column type: see sqlTypeInfo.
For the numeric values returned by sqlColumns(special=TRUE) see
https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqlspecialcolumns-function?view=sql-server-ver15:
the scope should always be 2 (the session) since that is the
scope requested in the call. For the PSEUDO_COLUMN column, the
possible values are 0 (unknown), 1 (no) and 2
(yes).
Michael Lapsley and Brian Ripley
odbcConnect, sqlQuery, sqlFetch,
sqlSave, sqlTables, odbcGetInfo
## Not run: ## example results from MySQL > channel <- odbcConnect("test") > sqlDrop(channel, "USArrests", errors = FALSE) # precautionary > sqlSave(channel, USArrests, addPK = TRUE) > sqlColumns(channel, "USArrests") TABLE_CAT TABLE_SCHEM TABLE_NAME COLUMN_NAME DATA_TYPE TYPE_NAME 1 ripley <NA> USArrests rownames 12 varchar 2 ripley <NA> USArrests Murder 8 double 3 ripley <NA> USArrests Assault 4 integer 4 ripley <NA> USArrests UrbanPop 4 integer 5 ripley <NA> USArrests Rape 8 double ... 12 more columns > sqlColumns(channel, "USArrests", special = TRUE) SCOPE COLUMN_NAME DATA_TYPE TYPE_NAME COLUMN_SIZE BUFFER_LENGTH 1 2 rownames 12 varchar 255 255 DECIMAL_DIGITS PSEUDO_COLUMN 1 NA 1 > sqlPrimaryKeys(channel, "USArrests") TABLE_CAT TABLE_SCHEM TABLE_NAME COLUMN_NAME KEY_SEQ PK_NAME 1 <NA> <NA> USArrests rownames 1 PRIMARY > sqlDrop(channel, "USArrests") > close(channel) ## End(Not run)## Not run: ## example results from MySQL > channel <- odbcConnect("test") > sqlDrop(channel, "USArrests", errors = FALSE) # precautionary > sqlSave(channel, USArrests, addPK = TRUE) > sqlColumns(channel, "USArrests") TABLE_CAT TABLE_SCHEM TABLE_NAME COLUMN_NAME DATA_TYPE TYPE_NAME 1 ripley <NA> USArrests rownames 12 varchar 2 ripley <NA> USArrests Murder 8 double 3 ripley <NA> USArrests Assault 4 integer 4 ripley <NA> USArrests UrbanPop 4 integer 5 ripley <NA> USArrests Rape 8 double ... 12 more columns > sqlColumns(channel, "USArrests", special = TRUE) SCOPE COLUMN_NAME DATA_TYPE TYPE_NAME COLUMN_SIZE BUFFER_LENGTH 1 2 rownames 12 varchar 255 255 DECIMAL_DIGITS PSEUDO_COLUMN 1 NA 1 > sqlPrimaryKeys(channel, "USArrests") TABLE_CAT TABLE_SCHEM TABLE_NAME COLUMN_NAME KEY_SEQ PK_NAME 1 <NA> <NA> USArrests rownames 1 PRIMARY > sqlDrop(channel, "USArrests") > close(channel) ## End(Not run)
Functions to copy tables or result sets from one database to another.
sqlCopy(channel, query, destination, destchannel = channel, verbose = FALSE, errors = TRUE, ...) sqlCopyTable(channel, srctable, desttable, destchannel = channel, verbose = FALSE, errors = TRUE)sqlCopy(channel, query, destination, destchannel = channel, verbose = FALSE, errors = TRUE, ...) sqlCopyTable(channel, srctable, desttable, destchannel = channel, verbose = FALSE, errors = TRUE)
channel, destchannel
|
connection handle as returned by
|
query |
any valid SQL statement |
destination, srctable, desttable
|
character: a database table name accessible from the connected DSN. |
verbose |
Display statements as they are sent to the server? |
errors |
if TRUE halt and display error, else return |
... |
additional arguments to be passed to |
sqlCopy as is like sqlQuery, but saves the output
of query in table destination on channel
destchannel.
sqlCopyTable copies the structure of srctable to
desttable on DSN destchannel. This is within the
limitations of the ODBC lowest common denominator. More precise
control is possible via sqlQuery.
See sqlGetResults.
Michael Lapsley and Brian Ripley
## Not run: ## example for a l/casing DBMS sqlSave(channel, USArrests, rownames = "state") query <- paste("select state, murder from usarrests", "where rape > 30", "order by murder") sqlCopy(channel, query, "HighRape", rownames = FALSE) sqlFetch(channel, "HighRape", rownames = "state", max = 5) sqlDrop(channel, "HighRape") ## End(Not run)## Not run: ## example for a l/casing DBMS sqlSave(channel, USArrests, rownames = "state") query <- paste("select state, murder from usarrests", "where rape > 30", "order by murder") sqlCopy(channel, query, "HighRape", rownames = FALSE) sqlFetch(channel, "HighRape", rownames = "state", max = 5) sqlDrop(channel, "HighRape") ## End(Not run)
sqlClear deletes all the rows of the table sqtable.
sqlDrop removes the table sqtable (if permitted).
sqlClear(channel, sqtable, errors = TRUE) sqlDrop(channel, sqtable, errors = TRUE)sqlClear(channel, sqtable, errors = TRUE) sqlDrop(channel, sqtable, errors = TRUE)
channel |
connection object as returned by |
sqtable |
character string: a database table name accessible from the
connected DSN. This can be a ‘dotted’ name of the form
|
errors |
logical: if |
These submit ‘TRUNCATE TABLE’ and ‘DROP TABLE’ SQL queries respectively.
‘Dotted’ table names are allowed on systems that support them
but the existence of the table is not checked and so attempting these
operations on a non-existent table will give a low-level error. (This
can be suppressed by opening the connection with interpretDot =
FALSE.)
The default ‘drop’ behaviour in Oracle is to move the table to the ‘recycle bin’: use
sqlQuery(channel, "PURGE recyclebin")
to empty the recycle bin.
The current user might not have privileges to allow these operations, and Actual Technologies' Mac OS X SQLite driver has a bug causing them silently to fail.
If errors = FALSE, a numeric value, invisibly.
Otherwise a character string or invisible().
Michael Lapsley and Brian Ripley
odbcConnect, sqlQuery, sqlFetch,
sqlSave, sqlTables, odbcGetInfo
Read some or all of a table from an ODBC database into a data frame.
sqlFetch(channel, sqtable, ..., colnames = FALSE, rownames = TRUE) sqlFetchMore(channel, ..., colnames = FALSE, rownames = TRUE)sqlFetch(channel, sqtable, ..., colnames = FALSE, rownames = TRUE) sqlFetchMore(channel, ..., colnames = FALSE, rownames = TRUE)
channel |
connection handle returned by |
sqtable |
a database table name accessible from the connected DSN. This should be either a literal character string or a character vector of length 1. |
... |
additional arguments to be passed to
|
colnames |
logical: retrieve column names from first row of table?
(For use when |
rownames |
either logical or character.
If logical, retrieve row names from the first column
( |
Note the ‘table’ includes whatever table-like objects are provided by the DBMS, in particular views and system tables.
sqlFetch by default retrieves the the entire contents of the table
sqtable. Rownames and column names are restored as indicated
(assuming that they have been placed in the table by the corresponding
arguments to sqlSave).
Alternatively, sqlFetch can fetch the first max rows, in
which case sqlFetchMore will retrieve further result rows,
provided there has been no other ODBC query on that channel in the
meantime.
These functions try to cope with the peculiar way the Excel ODBC
driver handles table names, and to quote Access table names which
contain spaces. Dotted table names, e.g. myschema.mytable, are
allowed on systems that support them, unless the connection was opened
with interpretDot = FALSE.
Useful additional parameters to pass to sqlQuery or
sqlGetResults include
max:limit on the number of rows to fetch, with
0 (the default) indicating no limit.
nullstring:character string to be used when reading
SQL_NULL_DATA character items from the database:
default NA_character_.
na.strings:character string(s) to be mapped to
NA when reading character data: default "NA".
as.is:as in sqlGetResults.
dec:The character for the decimal place to be assumed when converting character columns to numeric.
rows_at_time:Allow for multiple rows to be retrieved at
once. See sqlQuery.
A data frame on success, or a character or numeric error code (see
sqlQuery).
If the table name desired is not a valid SQL name (alphanumeric plus
_) and these functions are not able to interpret the name, you
can use sqlQuery with whatever quoting mechanism
your DBMS vendor provides (e.g. [ ] on some Microsoft
products and backticks on MySQL).
Michael Lapsley and Brian Ripley
sqlSave, sqlQuery,
odbcConnect, odbcGetInfo
## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests) sqlFetch(channel, "USArrests") # get the lot sqlFetch(channel, "USArrests", max = 20, rows_at_time = 10) sqlFetchMore(channel, max = 20) sqlFetchMore(channel) # get the rest sqlDrop(channel, "USArrests") close(channel) ## End(Not run)## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests) sqlFetch(channel, "USArrests") # get the lot sqlFetch(channel, "USArrests", max = 20, rows_at_time = 10) sqlFetchMore(channel, max = 20) sqlFetchMore(channel) # get the rest sqlDrop(channel, "USArrests") close(channel) ## End(Not run)
Submit an SQL query to an ODBC database, and retrieve the results.
sqlQuery(channel, query, errors = TRUE, ..., rows_at_time) sqlGetResults(channel, as.is = FALSE, errors = FALSE, max = 0, buffsize = 1000, nullstring = NA_character_, na.strings = "NA", believeNRows = TRUE, dec = getOption("dec"), stringsAsFactors = FALSE)sqlQuery(channel, query, errors = TRUE, ..., rows_at_time) sqlGetResults(channel, as.is = FALSE, errors = FALSE, max = 0, buffsize = 1000, nullstring = NA_character_, na.strings = "NA", believeNRows = TRUE, dec = getOption("dec"), stringsAsFactors = FALSE)
channel |
connection handle as returned by |
query |
any valid SQL statement. |
errors |
logical: if true halt and display error, else return |
... |
additional arguments to be passed to |
rows_at_time |
The number of rows to fetch at a time, between 1 and 1024. See ‘Details’. |
as.is |
which (if any) columns returned as character should be
converted to another type? Allowed values are as for
|
max |
limit on the number of rows to fetch, with |
buffsize |
an initial guess at the number of rows, used if
|
nullstring |
character string to be used when reading
|
na.strings |
character vector of strings to be mapped to
|
believeNRows |
logical. Is the number of rows returned by the ODBC connection believable? This might have been set to false when the channel was opened, and if so that setting cannot be overridden. |
dec |
The character for the decimal place to be assumed when converting character columns to numeric. |
stringsAsFactors |
logical: should columns returned as character and not
excluded by |
sqlQuery is the workhorse function of RODBC. It sends the SQL
statement query to the server, using connection channel
returned by odbcConnect, and retrieves (some or all of)
the results via sqlGetResults.
The term ‘query’ includes any valid SQL statement including
table creation, alteration, updates etc as well as ‘SELECT’s. The
sqlQuery command is a convenience wrapper that first calls
odbcQuery and then sqlGetResults. If
finer-grained control is needed, for example over the number of rows
fetched, additional arguments can be passed to sqlQuery or the
underlying functions called directly.
sqlGetResults is a mid-level function. It is called after a
call to sqlQuery or odbcQuery to retrieve waiting
results into a data frame. Its main use is with max set to
non-zero when it will retrieve the result set in batches with repeated
calls. This is useful for very large result sets which can be
subjected to intermediate processing.
Where possible sqlGetResults transfers data in binary form:
this happens for columns of (ODBC) SQL types double,
real, integer and smallint, and for binary SQL
types (which are transferred as lists of raw vectors, given class
"ODBC_binary"). All other SQL data types are converted to
character strings by the ODBC interface.
This paragraph applies only to SQL data types which are returned by
ODBC as character vectors. If when creating the connection (see
odbcConnect) DBMSencoding was set to a non-empty
value, the character strings are re-encoded. Then if as.is
is true for a column, it is returned as a character vector. Otherwise
(where detected) date, datetime and timestamp
values are converted to the "Date" or "POSIXct" class.
(Some drivers seem to confuse times with dates, so times may get
converted too. Also, some DBMSs (e.g. Oracle's) idea of date
is a date-time.) Remaining cases are converted by R using
type.convert. When character data are to be converted
to numeric data, the setting of options("dec") is used to map
the character used by the ODBC driver in setting decimal points—this
is set to a locale-specific value when RODBC is initialized if
it is not already set.
Using buffsize will yield a marginal increase in speed if set
to no less than the maximum number of rows when believeNRows =
FALSE. (If set too small it can result in unnecessarily high
memory use as the buffers will need to be expanded.)
Modern drivers should work (and work faster, especially if
communicating with a remote machine) with rows_at_time = 100,
the usual default, or more. (However, some drivers may mis-fetch
multiple rows, in which case set rows_at_time = 1 when creating
the connection.) However, if max is specified then this
may fetch too many rows and hence it could be reduced (but then this
setting applies to all subsequent fetches from that result set).
Another circumstance in which you might want to reduce
rows_at_time is if there are large character columns in the
result set: with the default value up to 6Mb of buffer for each such
column could be allocated to store intermediate results.
On success, a data frame (possibly with 0 rows) or character string.
On error, if errors = TRUE a character vector of error
message(s), otherwise an invisible integer error code -1
(general, call odbcGetErrMsg for details) or -2
(no data, which may not be an error as some SQL statements do return
no data).
Michael Lapsley and Brian Ripley
odbcConnect, sqlFetch,
sqlSave, sqlTables, odbcQuery
## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests, rownames = "State", verbose = TRUE) # options(dec=".") # optional, if DBMS is not locale-aware or set to ASCII ## note case of State, Murder, Rape are DBMS-dependent, ## and some drivers need column and table names double-quoted. sqlQuery(channel, paste("select State, Murder from USArrests", "where Rape > 30 order by Murder")) close(channel) ## End(Not run)## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests, rownames = "State", verbose = TRUE) # options(dec=".") # optional, if DBMS is not locale-aware or set to ASCII ## note case of State, Murder, Rape are DBMS-dependent, ## and some drivers need column and table names double-quoted. sqlQuery(channel, paste("select State, Murder from USArrests", "where Rape > 30 order by Murder")) close(channel) ## End(Not run)
Write or update a table in an ODBC database.
sqlSave(channel, dat, tablename = NULL, append = FALSE, rownames = TRUE, colnames = FALSE, verbose = FALSE, safer = TRUE, addPK = FALSE, typeInfo, varTypes, fast = TRUE, test = FALSE, nastring = NULL) sqlUpdate(channel, dat, tablename = NULL, index = NULL, verbose = FALSE, test = FALSE, nastring = NULL, fast = TRUE)sqlSave(channel, dat, tablename = NULL, append = FALSE, rownames = TRUE, colnames = FALSE, verbose = FALSE, safer = TRUE, addPK = FALSE, typeInfo, varTypes, fast = TRUE, test = FALSE, nastring = NULL) sqlUpdate(channel, dat, tablename = NULL, index = NULL, verbose = FALSE, test = FALSE, nastring = NULL, fast = TRUE)
channel |
connection handle returned by |
dat |
a data frame. |
tablename |
character: a database table name accessible from
the connected DSN. If missing, the name of |
index |
character. Name(s) of index column(s) to be used. |
append |
logical. Should data be appended to an existing table? |
rownames |
either logical or character. If logical, save the row
names as the first column |
colnames |
logical: save column names as the first row of table? |
verbose |
display statements as they are sent to the server? |
safer |
logical. If true, create a non-existing table but only
allow appends to an existing table. If false, allow |
addPK |
logical. Should rownames (if included) be specified as a primary key? |
typeInfo |
optional list of DBMS datatypes. Should have elements
named |
varTypes |
an optional named character vector giving the DBMSs datatypes to be used for some (or all) of the columns if a table is to be created. |
fast |
logical. If false, write data a row at a time. If true,
use a parametrized |
test |
logical: if |
nastring |
optional character string to be used for writing
|
sqlSave saves the data frame dat in the table
tablename. If the table exists and has the appropriate
structure it is used, or else it is created anew. If a new table is
created, column names are remapped by removing any characters which
are not alphanumeric or _, and the types are selected by
consulting arguments varTypes and typeInfo, then looking
the driver up in the database used by getSqlTypeInfo or
failing that by interrogating sqlTypeInfo.
If rownames = TRUE the first column of the table will be the
row labels with colname rowname: rownames can also be a
string giving the desired column name (see ‘Examples’). If
colnames is true, the column names are copied into row 1. This
is intended for cases where case conversion alters the original column
names and it is desired that they are retained. Note that there are
drawbacks to this approach: it presupposes that the rows will be
returned in the correct order; not always valid. It will also cause
numeric columns to be returned as factors.
Argument addPK = TRUE causes the row names to be marked as a
primary key. This is usually a good idea, and may allow database
updates to be done. However, the ODBC drivers for some DBMSs
(e.g. Access) do not support primary keys, and earlier versions of the
PostgreSQL ODBC driver generated internal memory corruption if this
option is used.
sqlUpdate updates the table where the rows already exist. Data
frame dat should contain columns with names that map to (some
of) the columns in the table. It also needs to contain the column(s)
specified by index which together identify the rows to be
updated. If index = NULL, the function tries to identify such
columns. First it looks for a primary key for the table, then for the
column(s) that the database regards as the optimal for defining a row
uniquely (these are returned by sqlColumns(special =
TRUE): if this returns a pseudo-column it cannot be used as we do not
have values for the rows to be changed). Finally, the row names are
used if they are stored as column "rownames" in the table.
When fast = TRUE, NAs are always written as SQL nulls in
the database, and this is also the case if fast = FALSE and
nastring = NULL (its default value). Otherwise nastring
gives the character string to be sent to the driver when NAs
are encountered: for all but the simplest applications it will be
better to prepare a data frame with non-null missing values already
substituted.
If fast = FALSE all data are sent as character strings.
If fast = TRUE, integer and double vectors are sent as types
SQL_C_SLONG and SQL_C_DOUBLE respectively. Some drivers
seem to require fast = FALSE to send other types,
e.g. datetime. SQLite's approach is to use the data to determine
how it is stored, and this does not work well with fast = TRUE.
If tablename contains ‘.’ and neither catalog nor
schema is supplied, an attempt is made to interpret
qualifier.table names as table table
in schema qualifier (and for MySQL ‘schema’ means
‘database’). (This can be suppressed by opening the connection with
interpretDot = FALSE.)
1 invisibly for success (and failures cause errors).
sqlSave(safer = FALSE) uses the ‘great white shark’
method of testing tables (bite it and see). The logic will
unceremoniously DROP the table and create it anew with its own
choice of column types in its attempt to find a writable
solution. test = TRUE will not necessarily predict this
behaviour. Attempting to write indexed columns or writing to
pseudo-columns are less obvious causes of failed writes followed by a
DROP. If your table structure is precious it is up to you back
it up.
Michael Lapsley and Brian Ripley
sqlFetch, sqlQuery,
odbcConnect, odbcGetInfo
## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests, rownames = "state", addPK=TRUE) sqlFetch(channel, "USArrests", rownames = "state") # get the lot foo <- cbind(state=row.names(USArrests), USArrests)[1:3, c(1,3)] foo[1,2] <- 222 sqlUpdate(channel, foo, "USArrests") sqlFetch(channel, "USArrests", rownames = "state", max = 5) sqlDrop(channel, "USArrests") close(channel) ## End(Not run)## Not run: channel <- odbcConnect("test") sqlSave(channel, USArrests, rownames = "state", addPK=TRUE) sqlFetch(channel, "USArrests", rownames = "state") # get the lot foo <- cbind(state=row.names(USArrests), USArrests)[1:3, c(1,3)] foo[1,2] <- 222 sqlUpdate(channel, foo, "USArrests") sqlFetch(channel, "USArrests", rownames = "state", max = 5) sqlDrop(channel, "USArrests") close(channel) ## End(Not run)
List the table-like objects accessible from an ODBC connection. What objects are ‘table-like’ depends on the DBMS, ODBC driver and perhaps even the configuration settings: in particular some connections report system tables and some do not.
sqlTables(channel, errors = FALSE, as.is = TRUE, catalog = NULL, schema = NULL, tableName = NULL, tableType = NULL, literal = FALSE)sqlTables(channel, errors = FALSE, as.is = TRUE, catalog = NULL, schema = NULL, tableName = NULL, tableType = NULL, literal = FALSE)
channel |
connection handle as returned by
|
errors |
if |
as.is |
as in |
catalog, schema, tableName, tableType
|
|
literal |
logical: (where supported) should arguments be interpreted literally or including wildcards? |
A data frame on success, or character/numeric on error depending on
the errors argument. (Use sqlGetResults for
further details of errors.)
The column names depend on the database, containing a third column
TABLE_NAME (not always in upper case): however, they are
supposed to be always in the same order.
The first column is the ‘catalog’ or (in ODBC2 parlance)
‘qualifier’, the second the ‘schema’ or (ODBC2)
‘owner’, the third the name, the fourth the table type (one of
"TABLE", "VIEW", "SYSTEM TABLE", "ALIAS",
"SYNONYM", or a driver-specific type name) and the fifth
column any remarks.
Oddly, the Microsoft Excel driver considers worksheets to be system tables, and named ranges to be tables.
Whether the additional arguments are implemented and what they do is
driver-specific. The standard SQL wildcards are underscore to
match a single character and percent to match zero or more
characters (and often backslash will escape these): these are not used
for table types. All of these drivers interpret wildcards in
tableName, and in catalog or schema where
supported.
Setting one of catalog or schema to "%" and the
other and tableName to "" should give a list of
available catalogs or schemas, whereas
catalog = "", schema = "", tableName = "", tableType = "%"
should list the supported table types.
For MySQL, catalog refers to a database whereas
schema is mostly ignored, and literal is ignored. To
list all databases use just catalog = "%". In the 5.1.x
driver, use catalog="db_name", tableName="%" to list the
tables in another database, and to list the table types use the
form displayed above.
For PostgreSQL's ODBC driver catalog is ignored (except that
catalog = "" is required when listing schema or table types) and
literal works for both schema and for tableName.
SQLite ODBC ignores catalog and schema, except that the
displayed form is used to list table types. So although it is
possible to attach databases and to refer to them by the dotted
name notation, it is apparently impossible to list tables on attached
databases.
Microsoft SQL Server 2008 interprets both catalog and schema.
With literal = TRUE it only finds tables if schema is
set (even to an empty string). Schemas are only listed if they contain
objects.
Oracle's Windows ODBC driver finds no matches if anything non-empty is
supplied for the catalog argument. Unless a schema is
specified it lists tables in all schemas. It lists available table
types as just "TABLE" and "VIEW", but other types appear
in listings. With literal = TRUE it only finds tables if
schema is set (even to an empty string).
DB2 implements schemas but not catalogs. literal = TRUE has no
effect. In some uses case matters and upper-case names must be used
for schemas.
The Microsoft Access and Excel drivers interpret catalog as the
name of the Access .mdb or Excel .xls file (with the
path but without the extension): wildcards are interpreted in
catalog (for files in the same folder as the attached database)
and tableName. Using schema is an error except when
listing catalogs or table types. The Excel driver matched
tableType = "TABLE" (a named range) but not tableType =
"SYSTEM TABLE" (the type returned for worksheets).
The Actual Technologies Access/Excel driver ignores all the additional arguments.
Michael Lapsley and Brian Ripley
## Not run: > sqlTables(channel, "USArrests") ## MySQL example TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS 1 ripley USArrests TABLE ## PostgreSQL example TABLE_QUALIFIER TABLE_OWNER TABLE_NAME TABLE_TYPE REMARKS 1 ripley public usarrests TABLE ## Microsoft Access example > sqlTables(channel) TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS 1 C:\bdr\test <NA> MSysAccessObjects SYSTEM TABLE <NA> 2 C:\bdr\test <NA> MSysACEs SYSTEM TABLE <NA> 3 C:\bdr\test <NA> MSysObjects SYSTEM TABLE <NA> 4 C:\bdr\test <NA> MSysQueries SYSTEM TABLE <NA> 5 C:\bdr\test <NA> MSysRelationships SYSTEM TABLE <NA> 6 C:\bdr\test <NA> hills TABLE <NA> 7 C:\bdr\test <NA> USArrests TABLE <NA> ## End(Not run)## Not run: > sqlTables(channel, "USArrests") ## MySQL example TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS 1 ripley USArrests TABLE ## PostgreSQL example TABLE_QUALIFIER TABLE_OWNER TABLE_NAME TABLE_TYPE REMARKS 1 ripley public usarrests TABLE ## Microsoft Access example > sqlTables(channel) TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS 1 C:\bdr\test <NA> MSysAccessObjects SYSTEM TABLE <NA> 2 C:\bdr\test <NA> MSysACEs SYSTEM TABLE <NA> 3 C:\bdr\test <NA> MSysObjects SYSTEM TABLE <NA> 4 C:\bdr\test <NA> MSysQueries SYSTEM TABLE <NA> 5 C:\bdr\test <NA> MSysRelationships SYSTEM TABLE <NA> 6 C:\bdr\test <NA> hills TABLE <NA> 7 C:\bdr\test <NA> USArrests TABLE <NA> ## End(Not run)
Request information about data types in an ODBC database
sqlTypeInfo(channel, type = "all", errors = TRUE, as.is = TRUE)sqlTypeInfo(channel, type = "all", errors = TRUE, as.is = TRUE)
channel |
connection handle as returned by |
type |
The types of columns about which information is requested.
Possible values are |
errors |
logical: if true halt and display error, else return |
as.is |
as in |
sqlTypeInfo attempts to find the types of columns the database
supports: ODBC drivers are not required to support this (but all known
examples do). Where it is supported, it is used by
sqlSave to decide what column types to create when
creating a new table in the database.
A data frame on success, or character/numeric on error depending on
the errors argument. Use sqlGetResults for
further details of errors.
The columns returned may depend on the ODBC driver manager. For a fully ODBC 3 manager, see https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqlgettypeinfo-function?view=sql-server-ver15 the symbolic constants mentioned there will be returned as numbers (and the values of the numeric constants can be found in the ODBC headers such as ‘sql.h’ and ‘sqlext.h’).
Brian Ripley
## Not run: > names(sqlTypeInfo(channel)) [1] "TYPE_NAME" "DATA_TYPE" "COLUMN_SIZE" [4] "LITERAL_PREFIX" "LITERAL_SUFFIX" "CREATE_PARAMS" [7] "NULLABLE" "CASE_SENSITIVE" "SEARCHABLE" [10] "UNSIGNED_ATTRIBUTE" "FIXED_PREC_SCALE" "AUTO_UNIQUE_VALUE" [13] "LOCAL_TYPE_NAME" "MINIMUM_SCALE" "MAXIMUM_SCALE" [16] "SQL_DATATYPE" "SQL_DATETIME_SUB" "NUM_PREC_RADIX" [19] "INTERVAL_PRECISION" ## End(Not run)## Not run: > names(sqlTypeInfo(channel)) [1] "TYPE_NAME" "DATA_TYPE" "COLUMN_SIZE" [4] "LITERAL_PREFIX" "LITERAL_SUFFIX" "CREATE_PARAMS" [7] "NULLABLE" "CASE_SENSITIVE" "SEARCHABLE" [10] "UNSIGNED_ATTRIBUTE" "FIXED_PREC_SCALE" "AUTO_UNIQUE_VALUE" [13] "LOCAL_TYPE_NAME" "MINIMUM_SCALE" "MAXIMUM_SCALE" [16] "SQL_DATATYPE" "SQL_DATETIME_SUB" "NUM_PREC_RADIX" [19] "INTERVAL_PRECISION" ## End(Not run)