Question

I bulk load data into MS SQL. In order to do so effectively I temporarily disable FK constraints on a table (one table 8 constraints all of which have cascade delete “Set NULL”). Before I re-enable constraint checking I need to check for invalid foreign keys and set them to NULL.

How would I go about achieving this goal? Thanks.

Answer 1

UPDATE MyMainTable
SET TableAID = CASE WHEN TableA.ID IS NULL THEN NULL ELSE TableAID END,
    TableBID = CASE WHEN TableB.ID IS NULL THEN NULL ELSE TableBID END,
FROM MyMainTable
     LEFT JOIN TableA ON MyMainTable.TableAID = TableA.ID
     LEFT JOIN TableB ON MyMainTable.TableBID = TableB.ID