The SQL.H header file contains prototypes for the functions and features in the Core ODBC Interface conformance level. The SQLEXT.H header file contains prototypes for the functions and features in the Level 1 and Level 2 API conformance levels. The SQLTYPES.H header file contains type definitions and indicators for the SQL data types.
The header files all contain a #define, ODBCVER, that an application or driver can set to be compiled for different versions of ODBC.
To align with the ISO CLI and X/Open CLI, the header files contain aliases for the following information types used in calls to SQLGetInfo. In the following table, the column "ODBC name" indicates the ODBC name for the information type in Chapter 21, "ODBC API Reference." The column "Alias in header file" indicates the name that is used in the ISO CLI and the X/Open CLI. The actual numeric value of these manifest names is the same in both ODBC and the standard CLIs. These aliases enable a standards-compliant application or driver to compile with the ODBC 3.x header files.
These alias include expansions of abbreviations in the ODBC names, so that the names are more understandable. "MAX" is expanded to "MAXIMUM", "LEN" to "LENGTH", "MULT" to "MULTIPLE", "OJ" to "OUTER_JOIN", and "TXN" to "TRANSACTION."
| ODBC name | Alias in header file |
| SQL_MAX_CATALOG_NAME_LEN | SQL_MAXIMUM_CATALOG_NAME_ LENGTH |
| SQL_MAX_COLUMN_NAME_LEN | SQL_MAXIMUM_COLUMN_NAME_ LENGTH |
| SQL_MAX_COLUMNS_IN_GROUP_BY | SQL_MAXIMUM_COLUMNS_IN_ GROUP_BY |
| SQL_MAX_COLUMNS_IN_ORDER_BY | SQL_MAXIMUM_COLUMNS_IN_ ORDER_BY |
| SQL_MAX_COLUMNS_IN_SELECT | SQL_MAXIMUM_COLUMNS_IN_ SELECT |
| SQL_MAX_COLUMNS_IN_TABLE | SQL_MAXIMUM_COLUMNS_IN_ TABLE |
| SQL_MAX_CONCURRENT_ACTIVITIES | SQL_MAXIMUM_CONCURRENT_ ACTIVITIES |
| SQL_MAX_CURSOR_NAME_LEN | SQL_MAXIMUM_CURSOR_NAME_ LENGTH |
| SQL_MAX_DRIVER_CONNECTIONS | SQL_MAXIMUM_DRIVER_ CONNECTIONS |
| SQL_MAX_IDENTIFIER_LEN | SQL_MAXIMUM_IDENTIFIER_ LENGTH |
| SQL_MAX_SCHEMA_NAME_LEN | SQL_MAXIMUM_SCHEMA_NAME_ LENGTH |
| SQL_MAX_STATEMENT_LEN | SQL_MAXIMUM_STATEMENT_ LENGTH |
| SQL_MAX_TABLE_NAME_LEN | SQL_MAXIMUM_TABLE_NAME_ LENGTH |
| SQL_MAX_TABLES_IN_SELECT | SQL_MAXIMUM_TABLES_IN_ SELECT |
| SQL_MAX_USER_NAME_LEN | SQL_MAXIMUM_USER_NAME_ LENGTH |
| SQL_MULT_RESULT_SETS | SQL_MULTIPLE_RESULT_SETS |
| SQL_OJ_CAPABILITIES | SQL_OUTER_JOIN_CAPABILITIES |
| SQL_TXN_CAPABLE | SQL_TRANSACTION_CAPABLE |
| SQL_TXN_ISOLATION_OPTION | SQL_TRANSACTION_ISOLATION_ OPTION |