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The VAR_POP SQL Function in MySQL and MariaDB - Population standard variance

VAR_POPSyntax:VAR_POP(Expression or column)
Return value:FLOAT
Synonyms:VARIANCE
Function type:Aggregate function, Window function
Function Description

The VAR_POP() function returns the population standard variance of "Expression or column".

The calculation performs the following steps: Finds the mean for the set. For each number, subtract the mean and square the result. Calculates the average of the resulting differences.

When evaluating string arguments, the function returns 0.

Using a DISTINCT clause will result in an error.

For ENUM fields, the standard variance of the positions of the values ​​in their lists is calculated.

For SET fields, the standard variance of the binary positions of the values ​​in their lists is calculated = POW(2, Position-1).

As an aggregate function, the VAR_POP() function can be used with a GROUP BY clause.

VAR_POP() can be used as a window function.

The VAR_POP() function returns NULL if no result is found.

SQL Examples for the VAR_POP function

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DROP TABLE IF EXISTS `test_table`;
    
CREATE TABLE `test_table` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  `type` enum('First','Second','Third','Last'DEFAULT NULL,
  `set` set('First','Second','Third','Last'DEFAULT NULL,
  `num` int(11) NOT NULL DEFAULT 0,
  `price` decimal(10,2) NOT NULL DEFAULT 0.00,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=latin1;

INSERT INTO `test_table` (`id`,`name`,`type`,`set`,`num`,`price`VALUES 
(1,'Art 1','First','Last',1,10.50),
(2,'Art 2','Second','First,Last',3,12.50),
(3,'Art 3','Second','Second,Last',2,15.50),
(4,'Art 4','Third','First,Second',5,25.50),
(5,'Art 5','Last','First,Last',2,5.50),
(6,'Art 6','First','First',12,1.50),
(7,'Art 7','Third','First,Third',20,1.75),
(8,'Art 8','Last','Second,Third',100,11.90);

select * from `test_table`;

select var_pop(name) from test_table;

select var_pop(num),var_pop(price),var_pop(`type`),var_pop(`set`from test_table;
select var_pop(num),var_pop(price) from test_table where id>8;

/* as Window function */

SELECT name, `type`, price, var_pop(price) 
  OVER (PARTITION BY `type`AS `var_pop` FROM test_table;

id
name
type
set
num
price
int(11)varchar(20) LATIN1enum LATIN1set LATIN1int(11)decimal(10,2)
1Art 1FirstLast110.50
2Art 2SecondFirst,Last312.50
3Art 3SecondSecond,Last215.50
4Art 4ThirdFirst,Second525.50
5Art 5LastFirst,Last25.50
6Art 6FirstFirst121.50
7Art 7ThirdFirst,Third201.75
8Art 8LastSecond,Third10011.90
var_pop(name)
double(23)
0
var_pop(num)
var_pop(price)
var_pop(`type`)
var_pop(`set`)
double(26)double(26)double(17)double(17)
994.859454.8087111.25008.9844
var_pop(num)
var_pop(price)
double(26)double(26)
NULLNULL
name
type
price
var_pop
test_table
varchar(20) LATIN1
test_table
enum LATIN1
test_table
decimal(10,2)

double(26)
Art 6First1.5020.250000
Art 1First10.5020.250000
Art 3Second15.502.250000
Art 2Second12.502.250000
Art 4Third25.50141.015625
Art 7Third1.75141.015625
Art 8Last11.9010.240000
Art 5Last5.5010.240000
The examples were created with the MyWAY SQL manager: Download

How to use the VAR_POP() function in MySQL and MariaDB databases

The VAR_POP() function (Population Standard Variance) in MySQL and MariaDB is used to calculate the population variance of a set of values ​​from table columns or expressions in SQL queries and provides a measure of how values ​​in a population are distributed around the mean by representing spread of data points. The population variance measures the average of the squared deviations from the population mean and the function assumes that it has access to the entire data.

VAR_POP() is used in statistical analysis to calculate the population variance of a set of values, for example also to compare the spread of values ​​between different datasets. This allows consistency or variability of data from different groups to be evaluated and compared. In addition, population variance is applied to monitor and improve process quality to identify variations or trends by analyzing variance over time. In financial and investment analysis, population variance can be used to assess risk. It is a measure of the spread of returns or prices. Higher variance values ​​mean higher risk.
UUIDUUID_SHORTUUID_TO_BINVAR_POPVAR_SAMPVARIANCEVERSION

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Aggregate functionsWindow functionsJSON functionsGeometric functions
Sequence functionsInformation functionsDynamic ColumnsMiscellaneous functions
More information about the VAR_POP SQL function: mysql.com and mariadb.com
Updated: 2023-09-17ImprintContactTerms & conditionsPrivacy & CookiesUpdatesSitemapFacebookLinkedinTwitterStatistics©2020-2024 Heino Cunze-Fischer