MySQL DATEDIFF from two different tables?

[viveleroi0]

I have two DATETIME fields, each in a different table in MySQL 4.1.7. I want to find the number of days bewteen them, how can I?

DATEDIFF doesn't want to work with this setup:

SELECT DATEDIFF(table1.row1, table2.row2)

I get an error saying table1 is an unknown table, thought I have verified it does exist (I do not use the actual table/field names in the above example).

How can I get this to work?

[nemonoman]

You'll need more than that. Your FROM clause is missing, which is why the error says 'Huh?' -- you haven't told it where to look.

SELECT DATEDIFF(table1.row1, table2.row2)
FROM table1, table2
WHERE table1.something=table2.something

If you generate these rows with previous queries, you CAN say:

$result=mysql_query("
SELECT DATEDIFF('$sometable1result', '$sometable2result')");

and retrieve the result.

In this case, you are asking the database to return data from two constants, not from two table rows.