Mysql - selecting year from a unix timestamp

Question

I am using this:

SELECT FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS year FROM table_name WHERE year = 2009;

but it gives me an error:

Unknown column 'year' in 'where clause'SELECT FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS year FROM table_name WHERE year = 2009

Both "my_unix_timestamp_column" and "table_name" are correct, i dont know why it gives me this!!!

I'm using PHP 5.3.0

Solution 1

I'm not quite sure whether this is due to YEAR being a reserved word in MySQL or because it wants you to do something along the lines of:

SELECT
  FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS year
FROM
  table_name
WHERE
  FROM_UNIXTIME(my_unix_timestamp_column, '%Y') = 2009;

Can't remember whether the last issue is only relevant to GROUPings :S

Solution 2

SELECT  FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS `year`
FROM    table_name
HAVING  `year` = 2009

Unlike WHERE clause, HAVING clause can reference the SELECT clause aliases.

More index efficient way would be:

SELECT  FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS `year`
FROM    table_name
WHERE   my_unix_timestamp_column >= UNIX_TIMESTAMP('2009-01-01')
        AND my_unix_timestamp_column < UNIX_TIMESTAMP('2010-01-01')

Solution 3

Another alternative, avoiding repetition of a biggish function call:

SELECT year
  FROM (SELECT FROM_UNIXTIME(my_unix_timestamp_column, '%Y') AS year
          FROM table_name) AS list_of_years
 WHERE year = 2009;

You might still need to use back-quotes around the word 'year' to avoid conflicts with YEAR as a keyword. The optimizer should not need to create an intermediate table to answer this query.