SQLPrimaryKeys
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
A table might have a column or columns that can serve as unique row identifiers, and tables created without a PRIMARY KEY constraint return an empty result set to SQLPrimaryKeys. The ODBC function SQLSpecialColumns reports row identifier candidates for tables without primary keys.
SQLPrimaryKeys returns SQL_SUCCESS whether or not values exist for CatalogName, SchemaName, or TableName parameters. SQLFetch returns SQL_NO_DATA when invalid values are used in these parameters.
SQLPrimaryKeys can be executed on a static server cursor. An attempt to execute SQLPrimaryKeys on an updatable (dynamic or keyset) cursor will return SQL_SUCCESS_WITH_INFO indicating that the cursor type has been changed.
The SQL Server Native Client ODBC driver supports reporting information for tables on linked servers by accepting a two-part name for the CatalogName parameter: Linked_Server_Name.Catalog_Name.
SQLPrimaryKeys and Table-Valued Parameters
If the statement attribute SQL_SOPT_SS_NAME_SCOPE has the value SQL_SS_NAME_SCOPE_TABLE_TYPE, rather than its default value of SQL_SS_NAME_SCOPE_TABLE, SQLPrimaryKeys will return information about primary key columns of table types. For more information on SQL_SOPT_SS_NAME_SCOPE, see SQLSetStmtAttr.
For more information about table-valued parameters, see Table-Valued Parameters (ODBC).