MySQL/SQL: Group by date only on a Datetime column

sql mysql
fmsf picture fmsf · Dec 14, 2008 · Viewed 242.9k times · Source

Having a table with a column like: mydate DATETIME ...

I have a query such as:

SELECT SUM(foo), mydate FROM a_table GROUP BY a_table.mydate;

This will group by the full datetime, including hours and minutes. I wish to make the group by, only by the date YYYY/MM/DD not by the YYYY/MM/DD/HH/mm.

Anyone know how to do this? I can still do it (as I am atm), dynamically in my code, but I'm cleaning trash code and this can be made through the SQL I just can't find out how :(.

Answer

Michael Haren picture Michael Haren · Dec 14, 2008

Cast the datetime to a date, then GROUP BY using this syntax:

SELECT SUM(foo), DATE(mydate) FROM a_table GROUP BY DATE(a_table.mydate);

Or you can GROUP BY the alias as @orlandu63 suggested:

SELECT SUM(foo), DATE(mydate) DateOnly FROM a_table GROUP BY DateOnly;

Though I don't think it'll make any difference to performance, it is a little clearer.

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