STDDEV_SAMP¶
Returns the sample standard deviation of values.
Note
Aliases to this function include STDDEV
and STDEV
for compatibility.
See also: STDDEV_POP
Syntax¶
-- As an aggregate
STDDEV_SAMP( expr )
STDDEV( expr )
STDEV( expr )
-- As a window function
STDDEV_SAMP ( expr ) OVER (
[ PARTITION BY value_expression [, ...] ]
[ ORDER BY value_expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ frame_clause ]
)
Arguments¶
Parameter |
Description |
---|---|
|
Numeric expression |
Returns¶
Returns the standard deviation with type DOUBLE
.
Notes¶
When all rows contain
NULL
values, the function returnsNULL
.The function also returns
NULL
when only one value is non-NULL
.
Examples¶
For these examples, assume a table named nba
, with the following structure:
CREATE TABLE nba
(
"Name" text,
"Team" text,
"Number" tinyint,
"Position" text,
"Age" tinyint,
"Height" text,
"Weight" real,
"College" text,
"Salary" float
);
Here’s a peek at the table contents (Download nba.csv
):
Avery Bradley |
Boston Celtics |
0 |
PG |
25 |
2-Jun |
180 |
Texas |
7730337 |
---|---|---|---|---|---|---|---|---|
Jae Crowder |
Boston Celtics |
99 |
SF |
25 |
6-Jun |
235 |
Marquette |
6796117 |
John Holland |
Boston Celtics |
30 |
SG |
27 |
5-Jun |
205 |
Boston University |
|
R.J. Hunter |
Boston Celtics |
28 |
SG |
22 |
5-Jun |
185 |
Georgia State |
1148640 |
Jonas Jerebko |
Boston Celtics |
8 |
PF |
29 |
10-Jun |
231 |
5000000 |
|
Amir Johnson |
Boston Celtics |
90 |
PF |
29 |
9-Jun |
240 |
12000000 |
|
Jordan Mickey |
Boston Celtics |
55 |
PF |
21 |
8-Jun |
235 |
LSU |
1170960 |
Kelly Olynyk |
Boston Celtics |
41 |
C |
25 |
Jul-00 |
238 |
Gonzaga |
2165160 |
Terry Rozier |
Boston Celtics |
12 |
PG |
22 |
2-Jun |
190 |
Louisville |
1824360 |
Simple standard deviation¶
t=> SELECT AVG("Age"), STDDEV_SAMP("Age") FROM nba;
avg | stddev_samp
----+------------
26 | 4.404
Combine stddev
with other aggregates¶
t=> SELECT "Age", AVG("Salary"), STDDEV_SAMP("Salary"), STDDEV_POP("Salary") FROM nba GROUP BY 1;
Age | avg | stddev_samp | stddev_pop
----+----------+--------------+-------------
19 | 1930440 | 279165.7572 | 197400
20 | 2725790 | 1510913.4308 | 1470615.1437
21 | 2067379 | 1412350.3607 | 1374680.8959
22 | 2357963 | 1517378.326 | 1487911.8642
23 | 2034746 | 2728292.0728 | 2693086.8292
24 | 3785300 | 4803383.8083 | 4749713.0309
25 | 3930867 | 4558462.9038 | 4506364.4739
26 | 6866566 | 6100470.7879 | 6015145.316
27 | 6676741 | 6831984.073 | 6746043.7454
28 | 5110188 | 4316626.5733 | 4244073.0603
29 | 6224177 | 4870705.8411 | 4779656.5821
30 | 7061858 | 5408669.6434 | 5317761.1581
31 | 8511396 | 7170163.4693 | 7005310.0889
32 | 7716958 | 7451335.8768 | 7159011.944
33 | 3930739 | 4354293.0145 | 4195901.738
34 | 7606030 | 5653035.0228 | 5362939.9094
35 | 3461739 | 2364690.175 | 2211965.1152
36 | 2238119 | 1550061.2451 | 1470517.2142
37 | 12777778 | 10715167.374 | 8748897.5249
38 | 1840041 | 1496660.6556 | 1296146.1486
39 | 2517872 | 2220522.4752 | 1570146.5
40 | 4666916 | 4155420.6792 | 3392886.7769