Question

SELECT COUNT(*) FROM area
WHERE ROUND(SQRT(POWER(('71' - coords_x), 2) +
                 POWER(('97' - coords_y), 2))) <= 17

==> 51

SELECT COUNT(*) FROM area
WHERE ROUND(SQRT(POWER((71 - coords_x), 2) +
                 POWER((97 - coords_y), 2))) <= 17

==> 22

coords_x and coords_y are both TINYINT fields containing values in the range [1, 150]. Usually MySQL doesn’t care if numbers are quoted or not.. but apparently it does in this case.

The question is just: Why?

Answer 1

MySQL always cares about data types. What happens is that your code relies in automatic type casting and performs math on strings (which can hold a number or not). This can lead to all sort of unpredictable results:

SELECT POW('Hello', 'World') -- This returns 1

To sum up: you need to learn and use the different data types MySQL offers. Otherwise, your application will never do reliable calculations.

Update:

One more hint:

TINYINT[(M)] [UNSIGNED] [ZEROFILL]

A very small integer. The signed range
is -128 to 127. The unsigned range is
0 to 255.

URL:
http://dev.mysql.com/doc/refman/5.1/en/numeric-type-overview.html

I hope you are not trying to store 150 in a signed tinyint column.