COVAR_SAMP¶
Returns the sample covariance of value pairs.
See also: COVAR_POP
Syntax¶
-- As an aggregate
COVAR_SAMP( expr1, expr2 )
-- As a window function
COVAR_SAMP ( expr1, expr2 ) OVER (
[ PARTITION BY value_expression [, ...] ]
[ ORDER BY value_expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ frame_clause ]
)
Arguments¶
Parameter |
Description |
---|---|
|
Numeric expression |
Returns¶
Returns the sample covariance 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 covariance¶
t=> SELECT "Team", COVAR_SAMP("Age","Salary") FROM nba GROUP BY 1 ORDER BY 2 ASC;
Team | covar_samp
-----------------------+--------------
Cleveland Cavaliers | -9899969.4945
San Antonio Spurs | -7434481.0571
Oklahoma City Thunder | -3960471.5619
Detroit Pistons | -1407390.5429
Los Angeles Clippers | -1037225.7619
New Orleans Pelicans | -464825.0117
Utah Jazz | 997312.2524
Philadelphia 76ers | 1570272.6593
Sacramento Kings | 2470827.9429
Dallas Mavericks | 2591500.1095
Washington Wizards | 2601352.3905
Milwaukee Bucks | 2790831.8458
Orlando Magic | 3029242.3187
Golden State Warriors | 3591810.3571
Portland Trail Blazers | 4223202.2714
Denver Nuggets | 4271493.8132
Toronto Raptors | 4847589.7762
Minnesota Timberwolves | 4867005.0256
Charlotte Hornets | 5418069.4286
Houston Rockets | 5688478.081
Phoenix Suns | 5979617.881
Indiana Pacers | 6169271.6857
Boston Celtics | 6243718.6264
Brooklyn Nets | 6556855.7857
Chicago Bulls | 6971097.7714
Atlanta Hawks | 9492270.0714
Memphis Grizzlies | 10256905.0769
New York Knicks | 10949120.7333
Miami Heat | 14093744.6795
Los Angeles Lakers | 16500218.2