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stddev_samp

Description​

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:

image

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