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I want to write a query to fetch records in record table A and but not in table B. As per my current application design, if a record is present in A then it should be present in table B as well. But due to some interfacing issues, not all records of table A are present table B. Now I want to have all those records which are in A but not in B. How can I fetch those records? Any help is appreciated. TIA.

Pushpendra Yadav
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1 Answers1

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You can use NOT EXISTS, e.g.:

SELECT * 
FROM tableA a
WHERE NOT EXISTS (
    SELECT * FROM tableB b WHERE b.a_id = a.id
);
Darshan Mehta
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  • Awesome! it worked. But, in my scenario I'll need to check records like this: if records is present in A1 or A2 or A3 but not in B1 and B2. How can I do so? Thanks! – Pushpendra Yadav Jun 01 '17 at 20:06
  • You can use `UNION` in that case, e.g. `SELECT * FROM (SELECT * FROM A1 UNION SELECT * FROM A2 ) a WHERE NOT EXISTS (*uion query for B tables*)`. – Darshan Mehta Jun 01 '17 at 20:35