How can you tell if a table in DB2 has a Primary Key?
Disclaimer: I do not know DB2.

I simply googled these with "db2 table definition".

Source: 

SELECT * 
FROM SYSIBM.SYSTABLES TAB,SYSIBM.SYSCOLUMNS COL 
WHERE TAB.CREATOR = COL.TBCREATOR 
AND TAB.CREATOR = 'xxxx' 
AND TAB.NAME = 'xxxxxxxxxxxxx' 
AND TAB.NAME = COL.TBNAME 
AND TAB.TYPE = 'V' ( OR 'T' ) 
ORDER BY 1,2;


Source:

SELECT * FROM syscat.tabconst WHERE type = 'P';