stddev_samp

Returns the sample standard deviation of an expression. Since v2.5.10, this function can also be used as a window function.

Syntax

STDDEV_SAMP(expr)

Parameters

expr: the expression. If it is a table column, it must evaluate to TINYINT, SMALLINT, INT, BIGINT, LARGEINT, FLOAT, DOUBLE, or DECIMAL.

Return value

Returns a DOUBLE value. The formula is as follows, where n represents the row count of the table:

Examples

MySQL > select stddev_samp(scan_rows)
from log_statis
group by datetime;
+--------------------------+
| stddev_samp(`scan_rows`) |
+--------------------------+
|        2.372044195280762 |
+--------------------------+

See also

stddev

keyword

STDDEV_SAMP,STDDEV,SAMP