We can find the primary key of any table using the SYSIBM.SYSCOLUMNS table. The SYSIBM.SYSCOLUMNS is a DB2 system table which contains one row for every column of each table. It also contains the data related to the views. Below SQL query can be fired in order to find the primary key of a particular table.
SELECT NAME FROM SYSIBM.SYSCOLUMNS WHERE TBNAME = 'TAB1’ AND KEYSEQ > 0 ORDER BY KEYSEQ ASC;
We will use our table name in the TBNAME column of SYSCOLUMNS table using the WHERE clause and KEYSEQ > 0 will return only primary keys.