SQL DELETE with JOIN another table for WHERE condition

Question

I have to delete rows from guide_category that have no relation with guide table (dead relations).

Here is what I want to do, but it of cou

Answer 1

Try this sample SQL scripts for easy understanding,

CREATE TABLE TABLE1 (REFNO VARCHAR(10))
CREATE TABLE TABLE2 (REFNO VARCHAR(10))

--TRUNCATE TABLE TABLE1
--TRUNCATE TABLE TABLE2

INSERT INTO TABLE1 SELECT 'TEST_NAME'
INSERT INTO TABLE1 SELECT 'KUMAR'
INSERT INTO TABLE1 SELECT 'SIVA'
INSERT INTO TABLE1 SELECT 'SUSHANT'

INSERT INTO TABLE2 SELECT 'KUMAR'
INSERT INTO TABLE2 SELECT 'SIVA'
INSERT INTO TABLE2 SELECT 'SUSHANT'

SELECT * FROM TABLE1
SELECT * FROM TABLE2

DELETE T1 FROM TABLE1 T1 JOIN TABLE2 T2 ON T1.REFNO = T2.REFNO

Your case is:

   DELETE pgc
     FROM guide_category pgc 
LEFT JOIN guide g
       ON g.id_guide = gc.id_guide 
    WHERE g.id_guide IS NULL