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The VARIANCE SQL Function in MySQL and MariaDB - Calculation of Standard variance

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

The VARIANCE() 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 VARIANCE() function can be used with a GROUP BY clause.

VARIANCE() can be used as a window function.

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

SQL Examples for the VARIANCE 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 variance(name) from test_table;

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

/* as Window function */

SELECT name, `type`, price, variance(price) 
  OVER (PARTITION BY `type`AS `variance` 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
variance(name)
double(23)
0
variance(num)
variance(price)
variance(`type`)
variance(`set`)
double(26)double(26)double(17)double(17)
994.859454.8087111.25008.9844
variance(num)
variance(price)
double(26)double(26)
NULLNULL
name
type
price
variance
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 VARIANCE() function in MySQL and MariaDB databases

The VARIANCE() function in MySQL and MariaDB is used to calculate the population variance of a set of values ​​from 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.

The VARIANCE() function 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.
UUID_TO_BINVAR_POPVAR_SAMPVARIANCEVERSIONWEEKWEEKDAY

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COUNTCOUNT(Expression or column)
More about COUNT Function

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More about GROUP_CONCAT Function

JSON_ARRAYAGGJSON_ARRAYAGG(Expression or column)

JSON_OBJECTAGGJSON_OBJECTAGG(Expression or column)

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More about MAX Function

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More about MIN Function

SUMSUM(Expression or column)
More about SUM Function

STDSTD(Expression or column)
More about STD Function

STDDEVSTDDEV(Expression or column)
More about STDDEV Function

STDDEV_POPSTDDEV_POP(Expression or column)
More about STDDEV_POP Function

STDDEV_SAMPSTDDEV_SAMP(Expression or column)
More about STDDEV_SAMP Function

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More about VAR_POP Function

VAR_SAMPVAR_SAMP(Expression or column)
More about VAR_SAMP Function

Numeric functionsString functionsRegular ExpressionsDate and Time functions
Comparison functionsEncryption & CompressionConversion functionsNULL functions
Aggregate functionsWindow functionsJSON functionsGeometric functions
Sequence functionsInformation functionsDynamic ColumnsMiscellaneous functions
More information about the VARIANCE SQL function: mysql.com and mariadb.com
Updated: 2023-09-17ImprintContactTerms & conditionsPrivacy & CookiesUpdatesSitemapFacebookLinkedinTwitterStatistics©2020-2024 Heino Cunze-Fischer