mysql - Update table1 with count from table1 when count is null -

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i had query updated row in table1 count(*) table -

update t1 set a=(select count(b) t2 c=10 group c)) id=20

the problem if there no entries in t2 c=10, query fails select returns null or nothing. there way make work if sub-select statement returns null?

p.s. have tried using ifnull, looks doesn't work.

one of mysql's many curiosities that, if 1 drops group by clause (mysql implicitly group rows if aggregate function used in absence of explicit group by clause), return aggregated results if there no underlying records; in case of count() function, returns result of 0 desired:

update t1 set a=(select count(*) t2 c=10) id=20

see on sqlfiddle.


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