Can I do a mysql Select, Update and Delete in one query?

Question

Can I say that one of many ways to optimize mysql is to reduce the number of queries?

If that so, can I do this:

- Select "data" => $A from table X
- Update $A from table Y
- Delete $A from table X

in one query?

Solution 1

You can't reduce the number of queries - they all do different things - but you could reduce the number of round trips to the database and the number of parses by wrapping it all as a PLSQL function.

However you can't select the data after you've deleted it.....but consider:

CREATE PROCEDURE s_u_d(a)
BEGIN

UPDATE tab_x SET tab_x.avalue=1 WHERE tab_x.another=a;

DELETE FROM tab_y WHERE tab_y.avalue=a;

SELECT * 
FROM tab_x
WHERE tab_x.another=a;

END;

NB - you can also run multiple selects in the same procedure and handle multiple, different shaped result sets, e.g. see this page

Solution 2

NO,
only can combine

• DELETE and SELECT
• UPDATE and SELECT

This is not a proper way for mysql optimization simply
because each query come with different query cost.

And in myisam, it involve table level locking for write

Example for UPDATE and SELECT

/* this will update TABLE_A if ID in TABLE_B exist in TABLE_A */
UPDATE TABLE_A, TABLE_B
  SET TABLE_A.SOME_COLUMN=TABLE_B.SOME_COLUMN
WHERE TABLE_A.ID=TABLE_B.ID

/* or */
UPDATE TABLE_A
  SET SOME_COLUMN = (SELECT SOME_COLUMN_B FROM TABLE_B WHERE ... LIMIT 1)

Example for DELETE and SELECT

DELETE FROM TABLE_A WHERE TABLE_A IN(SELECT ID FROM TABLE_B)