[SOLVED] once, twice, ...

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for this test i create a table with:

$s = "CREATE TABLE test_math (x int not null, y int not null )";

then add some data, say:

$s = "INSERT INTO test_math VALUES (2, 1), (2, , (2, 3), (2, 5), (2, 7), (2, 4), (2, 6), (2, 2) ";

 

heres my first query...

$s = "SELECT x, y, POW(x,y) as z FROM test_math WHERE (POW(x,y) > 16) ORDER BY POW(x,y)";

i can refine it like this...

$s = "SELECT x, y, POW(x,y) as z FROM test_math WHERE (POW(x,y) > 16) ORDER BY z";

 

but is there a way to just do the math once?

 

say like this (no it doesnt work!)

$s = "SELECT x, y, POW(x,y) as z FROM test_math WHERE (z > 16) ORDER BY z";

[wildteen88]

Aliases cannot be used in a WHERE clause. Use HAVING instead:

$s = "SELECT x, y, POW(x,y) as z FROM test_math HAVING (z > 16) ORDER BY z";

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thats buzz, cheers...

 

but i dont seem to be finding any good info in the mysql manual on the HAVING bit, not seen that before and would of thought youd of used it at the lowest element, even though i cant see how thatd be...

 

once again cheers...

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ok, i should read more, http://dev.mysql.com/doc/refman/5.0/en/select.html