When your crew_comptrain_refresh procedure is run and picks up NULL values, it usually means:

• The source tables already contain NULLs.

• Your queries inside the procedure don't filter them out.

How to resolve:

• Add IS NOT NULL filters to your SELECT statements.

• Use NVL(column, 'default') or COALESCE(column, 'default') to replace NULLs if needed.

• Ensure INNER JOIN is used instead of LEFT JOIN if you expect mandatory matches.

• Add DBMS_OUTPUT.PUT_LINE statements to debug and find which variable/column is returning NULL.

To find the problematic columns:

• Run direct queries like SELECT * FROM table WHERE column IS NULL; to locate missing data.