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Re: MySQL subquery
Posted by: Øystein Grøvlen
Date: October 28, 2016 01:03AM

Hi,

According to the SQL standard, the GROUP BY clause can not refer to aliases from the SELECT list. This is because GROUP BY is locically processed before SELECT. See http://stackoverflow.com/questions/3841295/sql-using-alias-in-group-by for a discussion on this.

MySQL (and some other database systems) allows referring to SELECT aliases in the GROUP BY clause. However, original column names will take precedence over aliases. Hence, in your first query, GROUP BY refers to the original tsmark column of the derived table t. So the work around in your case is to either use another name for the alias, or to move the date formatting into the subquery.

Regards,

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway

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