Extension Level Functions - ODBC Driver for Teradata

SQLBindParameter accepts a null pointer for the parameter data (rgbValue) when the parameter length (pcbValue) is equal to SQL_NULL_DATA. The maximum number of parameters supported by SQLBindParameter is 256.

Stored procedures can contain up to 1024 parameters. Although the database stores and supports them, ODBC Driver for Teradata cannot execute stored procedures containing more than 256 parameters because of the SQLBindParameter restriction.

Default parameter (pcbValue= SQL_DEFAULT_PARAM) for procedures (macros) that rely on resolving the bind at SQL_DATA_AT_EXEC is not implemented.

Since ANSI defines column-level privileges, ODBC Driver for Teradata returns the column privileges associated with a table. When all columns in a table have a particular privilege, ODBC Driver for Teradata returns the value ALL as the column name.

SQLColumns returns column information for tables and views with up to 22 columns. SQLColumns requires SELECT privileges on the tables in question.

By default, SQLDescribeCol and SQLColAttribute return the column name instead of the database column title. If an application wants ODBC Driver for Teradata return the column title instead of the actual column name, then the option Use Column Names in the Teradata ODBC Driver Options dialog box must not be selected for the DSN used, or set DontUseTitles = No on the UNIX OS.

Returning the column title instead of the actual column name can cause problems for certain applications, such as Crystal Reports, because they expect to get the column name and not the column title.

SQLDescribeCol and SQLColAttribute return an SQL Type of SQL_TIME for columns in the result set that are defined as INTEGER FORMAT 99:99:99 or FLOAT FORMAT 99:99:99. These columns can be fetched into SQL_C_TIME data or any form where time data can be converted.

SQLColAttribute returns that a column is a currency type if the DBC FORMAT for that column contains dollar signs, such as FORMAT ‘$$$,$$9.99’. This can be useful to help an application know how to format the result data.

SQLDescribeParam returns metadata for a column or expression corresponding to a parameter marker associated with a prepared SQL statement. This metadata also is available in the fields of the Implementation Parameter Description (IPD). Refer to the ODBC Specification for a detailed description of SQLDescribeParam.

After an SQLExecute or SQLExecDirect, SQLRowCount can be called to get the DBC Activity count for any type of SQL statement, even for SELECT statements.

For portability, applications should not rely on this behavior, because other ODBC drivers might return -1 rather than the row count after a SELECT statement.

SQLSpecialColumns() works correctly for views only if the view is on a single table and there is exactly one unique index on the table.

SQLSpecialColumns() works correctly for tables.

SQLStatistics() retrieves information about the indexes on a table, and supplies cardinality statistics on the indexes, but the number of pages is estimated for indexes. The number of pages is returned correctly for the base table (a page is assumed to be 4096 bytes), but is set to 0 for views.

SQLStatistics() supplies precise cardinality statistics on the table itself only if SQL_ENSURE is set; otherwise, the cardinality on the base table is set to the largest cardinality from any index on the table (usually accurate if there are any unique indexes).

The only way to accurately get the cardinality of a table is for the driver to perform a SELECT COUNT(*) FROM table. Consequently, SQL_ENSURE can be quite slow.

When the function SQLStatistics() is called with the parameter value SQL_ENSURE, it is only accurate for small tables.

For larger tables, SQL_ENSURE could effectively make the table unusable for extended periods, so the SQL_QUICK method is used instead, which gives the approximate values for cardinality and pages that are sufficient for most applications.

In Windows, SQLStatistics() returns index information on a specified table so you can read or update using a view on the table. User-defined index names, using ODBC grammar, which were specified to create the index are returned by SQLStatistics() as an index name if the index name is still defined in the DSN entry in the Registry (IndexName0-9). ODBC-style named indexes were removed in ODBC Driver for Teradata 16.20.

For example, an index name MyIndex was used to create an index on table MyTable using ODBC grammar syntax.

Internally, Teradata created the index MyTable001 for the table, but SQLStatistics() returns MyIndex as the index name instead of MyTable001 since the DSN entry contains this index name for MyTable. On all other PCs, MyTable001 is returned as the index name.

ODBC Driver for Teradata returns the information as a result set on the specified hstmt.

In the result set description are:

• PRIVILEGE: Identifies the table privilege. Can be one of the following or a data source-specific privilege.
• SELECT: The grantee is permitted to retrieve data for one or more columns of the table.
• INSERT: The grantee is permitted to insert new rows containing data for one or more columns into to the table.
• UPDATE: The grantee is permitted to update the data in one or more columns of the table.
• DELETE: The grantee is permitted to delete rows of data from the table.
• REFERENCES: The grantee is permitted to refer to one or more columns of the table within a constraint (for example, a unique, referential, or table check constraint). The scope of action permitted the grantee by a given table privilege is data source-dependent. For example, the UPDATE privilege might permit the grantee to update all columns in a table on one data source and only those columns for which the grantor has the UPDATE privilege on another data source.