Conformance
Version Introduced: ODBC 1.0
Standards Compliance: X/Open
Summary
f90SQLSpecialColumns retrieves the following information about columns within a specified table:
Syntax
| f90SQLSpecialColumns | (StatementHandle, IdentifierType, CatalogName, SchemaName, TableName, Scope, Nullable, iRet) |
| integer(SQLHSTMT_KIND),intent(in):: | StatementHandle |
| integer(SQLSMALLINT_KIND),intent(in):: | IdentifierType |
| character(len=*),intent(in):: | CatalogName |
| character(len=*),intent(in):: | SchemaName |
| character(len=*),intent(in):: | TableName |
| integer(SQLSMALLINT_KIND),intent(in):: | Scope |
| integer(SQLSMALLINT_KIND),intent(in):: | Nullable |
| integer(SQLRETURN_KIND),intent(out):: | iRet |
Arguments
StatementHandle [Input]
Statement handle.
IdentifierType [Input]
Type of column to return. Must be one of the following values:
- SQL_BEST_ROWID: Returns the optimal column or set of columns that, by retrieving values from the column or columns, allows any row in the specified table to be uniquely identified. A column can be either a pseudo-column specifically designed for this purpose (as in Oracle ROWID or Ingres TID) or the column or columns of any unique index for the table.
- SQL_ROWVER: Returns the column or columns in the specified table, if any, that are automatically updated by the data source when any value in the row is updated by any transaction (as in SQLBase ROWID or Sybase TIMESTAMP).
CatalogName [Input]
Catalog name for the table. If a driver supports catalogs for some tables but not for others, such as when the driver retrieves data from different DBMSs, an empty string ("") denotes those tables that do not have catalogs. CatalogName cannot contain a string search pattern.
If the SQL_ATTR_METADATA_ID statement attribute is set to SQL_TRUE, CatalogName is treated as an identifier, and its case is not significant. If it is SQL_FALSE, CatalogName is an ordinary argument; it is treated literally, and its case is significant. For more information, see "Arguments in Catalog Functions" in Chapter 10.
SchemaName [Input]
Schema name for the table. If a driver supports schemas for some tables but not for others, such as when the driver retrieves data from different DBMSs, an empty string ("") denotes those tables that do not have schemas. SchemaName cannot contain a string search pattern.
If the SQL_ATTR_METADATA_ID statement attribute is set to SQL_TRUE, SchemaName is treated as an identifier, and its case is not significant. If it is SQL_FALSE, SchemaName is an ordinary argument; it is treated literally, and its case is significant.
TableName [Input]
Table name. This argument cannot be a null pointer. TableName cannot contain a string search pattern.
If the SQL_ATTR_METADATA_ID statement attribute is set to SQL_TRUE, TableName is treated as an identifier, and its case is not significant. If it is SQL_FALSE, TableName is an ordinary argument; it is treated literally, and its case is significant.
Scope [Input]
Minimum required scope of the rowid. The returned rowid may be of greater scope. Must be one of the following:
- SQL_SCOPE_CURROW: The rowid is guaranteed to be valid only while positioned on that row. A later reselect using rowid may not return a row if the row was updated or deleted by another transaction.
- SQL_SCOPE_TRANSACTION: The rowid is guaranteed to be valid for the duration of the current transaction.
- SQL_SCOPE_SESSION: The rowid is guaranteed to be valid for the duration of the session (across transaction boundaries).
Nullable [Input]
Determines whether to return special columns that can have a NULL value. Must be one of the following:
- SQL_NO_NULLS: Exclude special columns that can have NULL values. Note that some drivers cannot support SQL_NO_NULLS, and that these drivers will return an empty result set if SQL_NO_NULLS was specified. Applications should be prepared for this case, and request SQL_NO_NULLS only if it is absolutely required.
- SQL_NULLABLE: Return special columns even if they can have NULL values.
iRet [Output]
SQL_SUCCESS, SQL_SUCCESS_WITH_INFO, SQL_STILL_EXECUTING, SQL_ERROR, or SQL_INVALID_HANDLE.
Diagnostics
When f90SQLSpecialColumns returns SQL_ERROR or SQL_SUCCESS_WITH_INFO, an associated SQLSTATE value may be obtained by calling f90SQLGetDiagRec with a HandleType of SQL_HANDLE_STMT and a Handle of StatementHandle. The following table lists the SQLSTATE values commonly returned by f90SQLSpecialColumns and explains each one in the context of this function; the notation "(DM)" precedes the descriptions of SQLSTATEs returned by the Driver Manager. The return code associated with each SQLSTATE value is SQL_ERROR, unless noted otherwise.
| SQLSTATE | Error | Description |
| 01000 | General warning | Driver-specific informational message. (Function returns SQL_SUCCESS_WITH_INFO.) |
| 08S01 | Communication link failure | The communication link between the driver and the data source to which the driver was connected failed before the function completed processing. |
| 24000 | Invalid cursor state | A cursor was open on the StatementHandle
and f90SQLFetch or f90SQLFetchScroll
had been called. This error is returned by the Driver Manager if f90SQLFetch or f90SQLFetchScroll has not returned SQL_NO_DATA, and is returned by the driver if f90SQLFetch or f90SQLFetchScroll has returned SQL_NO_DATA. A cursor was open on the StatementHandle but f90SQLFetch or f90SQLFetchScroll had not been called. |
| 40001 | Serialization failure | The transaction was rolled back due to a resource deadlock with another transaction. |
| 40003 | Statement completion unknown | The associated connection failed during the execution of this function and the state of the transaction cannot be determined. |
| HY000 | General error | An error occurred for which there was no specific SQLSTATE and for which no implementation-specific SQLSTATE was defined. The error message returned by f90SQLGetDiagRec in the MessageText buffer describes the error and its cause. |
| HY001 | Memory allocation error | The driver was unable to allocate memory required to support execution or completion of the function. |
| HY008 | Operation canceled | Asynchronous processing was enabled for the StatementHandle.
The function was called and, before it completed execution, f90SQLCancel
was called on the StatementHandle. Then the function was called again on the StatementHandle. The function was called and, before it completed execution, f90SQLCancel was called on the StatementHandle from a different thread in a multithread application. |
| HY009 | Invalid use of null pointer | The TableName argument was a null
pointer. (DM) The SQL_ATTR_METADATA_ID statement attribute was set to SQL_TRUE, the CatalogName argument was a null pointer, and the SQL_CATALOG_NAME InfoType returns that catalog names are supported. (DM) The SQL_ATTR_METADATA_ID statement attribute was set to SQL_TRUE, and the SchemaName argument was a null pointer. |
| HY010 | Function sequence error | (DM) An asynchronously executing function (not
this one) was called for the StatementHandle and was still executing when this
function was called. (DM) f90SQLExecute, f90SQLExecDirect, f90SQLBulkOperations, or f90SQLSetPos was called for the StatementHandle and returned SQL_NEED_DATA. This function was called before data was sent for all data-at-execution parameters or columns. |
| HY013 | Memory management error | The function call could not be processed because the underlying memory objects could not be accessed, possibly because of low memory conditions. |
| HY090 | Invalid string or buffer length | (DM) The value of one of the length arguments
was less than 0, but not equal to SQL_NTS. The value of one of the length arguments exceeded the maximum length value for the corresponding name. The maximum length of each name may be obtained by calling f90SQLGetInfo with the InfoType values: SQL_MAX_CATALOG_NAME_LEN |
| HY097 | Column type out of range | (DM) An invalid IdentifierType value was specified. |
| HY098 | Scope type out of range | (DM) An invalid Scope value was specified. |
| HY099 | Nullable type out of range | (DM) An invalid Nullable value was specified. |
| HYC00 | Optional feature not implemented | A catalog was specified and the driver or data
source does not support catalogs. A schema was specified and the driver or data source does not support schemas. The combination of the current settings of the SQL_ATTR_CONCURRENCY and SQL_ATTR_CURSOR_TYPE statement attributes was not supported by the driver or data source. The SQL_ATTR_USE_BOOKMARKS statement attribute was set to SQL_UB_VARIABLE, and the SQL_ATTR_CURSOR_TYPE statement attribute was set to a cursor type for which the driver does not support bookmarks. |
| HYT00 | Timeout expired | The query timeout period expired before the data source returned the requested result set. The timeout period is set through f90SQLSetStmtAttr, SQL_ATTR_QUERY_TIMEOUT. |
| HYT01 | Connection timeout expired | The connection timeout period expired before the data source responded to the request. The connection timeout period is set through f90SQLSetConnectAttr, SQL_ATTR_CONNECTION_TIMEOUT. |
| IM001 | Driver does not support this function | (DM) The driver associated with the StatementHandle does not support the function. |
Comments
When the IdentifierType argument is SQL_BEST_ROWID, f90SQLSpecialColumns returns the column or columns that uniquely identify each row in the table. These columns can always be used in a select-list or WHERE clause. f90SQLColumns, which is used to return a variety of information on the columns of a table, does not necessarily return the columns that uniquely identify each row, or columns that are automatically updated when any value in the row is updated by a transaction. For example, f90SQLColumns might not return the Oracle pseudo-column ROWID. This is why f90SQLSpecialColumns is used to return these columns. For more information, see "Uses of Catalog Data" in Chapter 10.
Note: For more information about the general use, arguments, and returned data of ODBC catalog functions, see Chapter 10.
If there are no columns that uniquely identify each row in the table, f90SQLSpecialColumns returns a rowset with no rows; a subsequent call to f90SQLFetch or f90SQLFetchScroll on the statement returns SQL_NO_DATA.
If the IdentifierType, Scope, or Nullable arguments specify characteristics that are not supported by the data source, f90SQLSpecialColumns returns an empty result set.
If the SQL_ATTR_METADATA_ID statement attribute is set to SQL_TRUE, the CatalogName, SchemaName, and TableName arguments are treated as identifiers, so cannot be set to a null pointer in certain situations. (For more information, see "Arguments in Catalog Functions" in Chapter 10).
f90SQLSpecialColumns returns the results as a standard result set, ordered by SCOPE.
The following columns have been renamed for ODBC 3.0. The column name changes do not affect backward compatibility because applications bind by column number.
| ODBC 2.0 column | ODBC 3.0 column |
| PRECISION | COLUMN_SIZE |
| LENGTH | BUFFER_LENGTH |
| SCALE | DECIMAL_DIGITS |
To determine the actual length of the COLUMN_NAME column, an application can call f90SQLGetInfo with the SQL_MAX_COLUMN_NAME_LEN option.
The following table lists the columns in the result set. Additional columns beyond column 8 (PSEUDO_COLUMN) can be defined by the driver. An application should gain access to driver-specific columns by counting down from the end of the result set rather than specifying an explicit ordinal position. For more information, see "Data Returned by Catalog Functions" in Chapter 10.
| Column name | Column number | Data type | Comments |
| SCOPE (ODBC 1.0) |
1 | SQLSMALLINT_KIND | Actual scope of the rowid. Contains one of the following values: SQL_SCOPE_CURROW SQL_SCOPE_SESSIONNULL is returned when IdentifierType is SQL_ROWVER. For a description of each value, see the description of Scope in "Syntax" earlier in this section. |
| COLUMN_NAME (ODBC 1.0) |
2 | Character*(*) not NULL |
Column name. The driver returns an empty string for a column that does not have a name. |
| DATA_TYPE (ODBC 1.0) |
3 | SQLSMALLINT_KIND not NULL |
SQL data type. This can be an ODBC SQL data
type or a driver-specific SQL data type. For a list of valid ODBC SQL data types, see Chapter 4. For information about driver-specific SQL data types, see the driver's documentation. |
| TYPE_NAME (ODBC 1.0) |
4 | Character*(*) not NULL |
Data source - dependent data type name; for example, "CHAR", "CHARACTER*(*)", "MONEY", "LONG VARBINARY", or "CHAR ( ) FOR BIT DATA". |
| COLUMN_SIZE (ODBC 1.0) |
5 | SQLINTEGER_KIND | The size of the column on the data source. |
| BUFFER_LENGTH (ODBC 1.0) |
6 | SQLINTEGER_KIND | The length in bytes of data transferred on an f90SQLGetData or f90SQLFetch
operation if SQL_F_DEFAULT is specified. For numeric data, this size may be different than the size of the data stored on the data source. This value is the same as the COLUMN_SIZE column for character or binary data. |
| DECIMAL_DIGITS (ODBC 1.0) |
7 | SQLSMALLINT_KIND | The decimal digits of the column on the data source. NULL is returned for data types where decimal digits are not applicable. |
| PSEUDO_COLUMN (ODBC 2.0) |
8 | SQLSMALLINT_KIND | Indicates whether the column is a
pseudo-column, such as Oracle ROWID: SQL_PC_UNKNOWN Note: For maximum interoperability, pseudo-columns should not be quoted with the identifier quote character returned by f90SQLGetInfo. |
f90SQL catalog structure f90SQL_SPECIALCOLUMNS_INFO_STRUCT contains fields that correspond to the columns in the previous tables. Your application can call f90SQLBindCol with an argument of type f90SQL_SPECIALCOLUMNS_INFO_STRUCT and conveniently bind all the columns in the table to the corresponding fields in the catalog structure in a single operation. . See Chapter 10 for more information on how to use this structure.
After the application retrieves values for SQL_BEST_ROWID, the application can use these values to reselect that row within the defined scope. The SELECT statement is guaranteed to return either no rows or one row.
If an application reselects a row based on the rowid column or columns and the row is not found, then the application can assume that the row was deleted or the rowid columns were modified. The opposite is not true: even if the rowid has not changed, the other columns in the row may have changed.
Columns returned for column type SQL_BEST_ROWID are useful for applications that need to scroll forward and back within a result set to retrieve the most recent data from a set of rows. The column or columns of the rowid are guaranteed not to change while positioned on that row.
The column or columns of the rowid may remain valid even when the cursor is not positioned on the row; the application can determine this by checking the SCOPE column in the result set.
Columns returned for column type SQL_ROWVER are useful for applications that need the ability to check whether any columns in a given row have been updated while the row was reselected using the rowid. For example, after reselecting a row using rowid, the application can compare the previous values in the SQL_ROWVER columns to the ones just fetched. If the value in a SQL_ROWVER column differs from the previous value, the application can alert the user that data on the display has changed.
Related Subroutines
| For information about | See |
| Binding a buffer to a column in a result set | f90SQLBindCol |
| Canceling statement processing | f90SQLCancel |
| Returning the columns in a table or tables | f90SQLColumns |
| Fetching a single row or a block of data in a forward-only direction | f90SQLFetch |
| Fetching a block of data or scrolling through a result set | f90SQLFetchScroll |
| Returning the columns of a primary key | f90SQLPrimaryKeys |