I always forget how to do things like this.
I have a database table with birthdates and I want to find out how many people have the same age.
I m trying:
SELECT TIMESTAMPDIFF( YEAR, birthdate, CURDATE( ) ) AS age, COUNT( age )
FROM person
GROUP BY age
but get the error
Unknown column age in field list
How can I do a group by on a named column?
Aliases can t be used in group by clauses, nor can it be used in other columns in the select list (yes, this sucks).
SELECT TIMESTAMPDIFF( YEAR, birthdate, CURDATE( ) ) AS age, COUNT( TIMESTAMPDIFF( YEAR, birthdate, CURDATE( ) ))
FROM person
GROUP BY TIMESTAMPDIFF( YEAR, birthdate, CURDATE( ) )
Nevermind, I figured it out.
Ok, I need to use COUNT(*)
SELECT TIMESTAMPDIFF( YEAR, birthdate, CURDATE( ) ) AS age, COUNT( * )
FROM person
GROUP BY age
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