row deletion in mysql

Question

I have a table say incompatible which has two columns namely codeA and codeB. Now, I have two entries as A, B and B, A if A is incompatible to B. My question is how do I remove one of the rows from the table in mysql?

It would be better if you explain with a proper data set and expected results. — Shaharyar
– Shaharyar, Commented Feb 2, 2016 at 18:17
okay. Say I have a table which has two subject codes and the table has values say (A, B), (A, C), (A, D), (B, A), etc. Now how do I remove the (B, A) if (A, B) is already present? — Krishna Chaurasia
– Krishna Chaurasia, Commented Feb 2, 2016 at 18:19

Giorgos Betsos · Accepted Answer · 2016-02-02 18:25:00Z

3

Try this:

DELETE t1 FROM incompatible AS t1
INNER JOIN incompatible AS t2 ON t1.codeA = t2.codeB AND t2.codeB = t1.codeA 
WHERE t1.codeA > t1.codeB

Demo here

edited Feb 2, 2016 at 18:25

answered Feb 2, 2016 at 18:19

Giorgos Betsos

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