MySQL Tutorial/Math Numeric Functions/SQRT
SQRT(-16);
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mysql> mysql> SELECT SQRT(-16); +-----------+ | SQRT(-16) | +-----------+ | NULL | +-----------+ 1 row in set (0.00 sec) mysql></source>
SQRT(X) returns the square root of a non-negative number X.
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mysql> mysql> SELECT SQRT(4); +---------+ | SQRT(4) | +---------+ | 2 | +---------+ 1 row in set (0.00 sec) mysql> mysql> SELECT SQRT(20); +-----------------+ | SQRT(20) | +-----------------+ | 4.4721359549996 | +-----------------+ 1 row in set (0.00 sec) mysql></source>