# VARIANCE

Calculates the population variance value from a set of numbers.

`VARIANCE` has synonym `VAR_POP` which is equivalent. `VARIANCE` returns NULL if there are not matching rows.

May be used as a window function and with the frame clause.

## Syntax

### Aggregate Function

`VARIANCE ( expression )`

### Window Function & Window Frame Clause

`VARIANCE( [ DISTINCT ] expr ) OVER ( [PARTITION BY expr] [ORDER BY expr] [<window_frame_function>])`

## Arguments

• expression: any expression. This may be a column name, the result of another function, or a math operation.

A double.

## Examples

```CREATE TABLE player_scores(player_name VARCHAR(50), player_id VARCHAR(10),     1st_qtr_score DECIMAL(5,2), 2nd_qtr_score DECIMAL(5,2),     3rd_qtr_score DECIMAL(5,2), 4th_qtr_score DECIMAL(5,2),     yearly_total AS 1st_qtr_score + 2nd_qtr_score + 3rd_qtr_score + 4th_qtr_score PERSISTED DECIMAL(5,2));
INSERT INTO player_scores VALUES    ('Steve', '119','22.50','72.00', '63.00', '45.00'),    ('Jack', '432', '90.10', '78.00','88.20', '92.20'),    ('Jim', '779','75.00', '68.90','55.70', '72.00'),     ('Eve', '189','91.50', '88.10', '95.00', '94.50'),    ('Shelia','338', '75.60', '72.00', '81.10', '78.40'),    ('June', '521', '81.00', '87.30','76.80','82.20'),    ('Martin', '674','98.80', '95.10', '88.00', '96.40');```

### Aggregate Function

`SELECT VARIANCE(yearly_total) FROM player_scores;`
``````+------------------------+
| VARIANCE(yearly_total) |
+------------------------+
|            3258.486939 |
+------------------------+``````

### Window Function

`SELECT player_name, 3rd_qtr_score, 4th_qtr_score,ROUND(VARIANCE(3rd_qtr_score) OVER (ORDER BY player_name)) AS VARIANCEFROM player_scoresORDER BY player_name;`
``````+-------------+---------------+---------------+----------+
| player_name | 3rd_qtr_score | 4th_qtr_score | VARIANCE |
+-------------+---------------+---------------+----------+
| Eve         |         95.00 |         94.50 |        0 |
| Jack        |         88.20 |         92.20 |       12 |
| Jim         |         55.70 |         72.00 |      294 |
| June        |         76.80 |         82.20 |      222 |
| Martin      |         88.00 |         96.40 |      191 |
| Shelia      |         81.10 |         78.40 |      159 |
| Steve       |         63.00 |         45.00 |      175 |
+-------------+---------------+---------------+----------+``````

### Window Frame Clause

`SELECT player_name, 1st_qtr_score, 2nd_qtr_score,ROUND(VARIANCE(1st_qtr_score) OVER (ORDER BY player_name, 1st_qtr_score, 2nd_qtr_score ROWS UNBOUNDED PRECEDING)) AS VARIANCEFROM player_scoresORDER BY player_name;`
``````+-------------+---------------+---------------+----------+
| player_name | 1st_qtr_score | 2nd_qtr_score | VARIANCE |
+-------------+---------------+---------------+----------+
| Eve         |         91.50 |         88.10 |        0 |
| Jack        |         90.10 |         78.00 |        0 |
| Jim         |         75.00 |         68.90 |       56 |
| June        |         81.00 |         87.30 |       46 |
| Martin      |         98.80 |         95.10 |       70 |
| Shelia      |         75.60 |         72.00 |       77 |
| Steve       |         22.50 |         72.00 |      549 |
+-------------+---------------+---------------+----------+``````