更新表a和表b

Question

TABLEA ( id - gcoins )
TABLEB ( id - prezzo )

Should I do a kind of subtraction: at number/value of 'gcoins' subtract number/value of 'prezzo'.

I tried:

UPDATE TABLEA SET TABLEA.gcoins = TABLEA.gcoins - TABLEB.prezzo FROM TABLEA JOIN TABLEB ON TABLEA.id = TABLEB.id;

I read this same code in this site at question in the 2010 but not work.

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM TABLEA JOIN TABLEB ON TABLEA.id = TABLEB.id' at line 1

Answer 1

You wrote "UPDATE TABLEA.gcoins", and you don't need wrote again "FROM TABLEA.gcoins". Join goes after the UPDATE value, see this example above:

Try write: UPDATE (your table) JOIN (your join) ON (your join comparison) SET (your update) WHERE (your clausure if you want)

Answer 2

Try this rewrite.

UPDATE  TABLEA JOIN TABLEB
            ON TABLEA.id = TABLEB.id
SET     TABLEA.gcoins = TABLEA.gcoins - TABLEB.prezzo