# MySQL VAR_POP() function

## VAR_POP() function

MySQL VAR_POP() function returns the population standard variance of an expression. Population variance is a statistical measure that quantifies the average squared deviation of values from the mean in a dataset.

This function is useful in -

- VAR_POP() quantifies the spread or dispersion of values around the mean (average) in a dataset.
- The population variance helps you understand the variability or dispersion of data points within the entire population.
- When analyzing data, VAR_POP() helps assess the distribution of values and provides an indication of the typical deviation from the mean.
- Population variance is used in inferential statistics to make inferences or predictions about the entire population based on the characteristics of the sample.
- Population variance can use to compare the variability of different populations or datasets and assess their similarity or difference.
- Population variance is used to assess the significance of differences between groups or populations.
- Population variance is used to calculate confidence intervals for population parameters.

** Syntax**

VAR_POP(expr);

Where **expr** is an expression.

**MySQL Version:** 8.0

**Example: VAR_POP() function**

The following statement returns the population standard variance of 'total_cost' from purchase table.

Sample table: purchase

Code:

```
-- This query calculates the population variance of the 'total_cost' column in the 'purchase' table.
SELECT VAR_POP(total_cost)
-- This statement selects the population variance of the 'total_cost' column.
FROM purchase;
-- This part of the query specifies the table from which data is being retrieved, which is 'purchase'.
```

**Explanation:**

- The purpose of this SQL query is to compute the population variance of the 'total_cost' values in the 'purchase' table.
- SELECT VAR_POP(total_cost): This part of the query selects the population variance of the 'total_cost' column. Population variance measures how much the values in the dataset differ from the mean (average) of the population.
- FROM purchase: This part specifies the table from which the data is being selected, which is the 'purchase' table.
- The query will return a single value, which is the population variance of the 'total_cost' values in the 'purchase' table. This value provides insight into the degree of spread or dispersion of the 'total_cost' values around the mean for the entire population represented by the 'purchase' table.

Output:

mysql> SELECT VAR_POP(total_cost) -> FROM purchase; +---------------------+ | VAR_POP(total_cost) | +---------------------+ | 99472.222222 | +---------------------+ 1 row in set (0.00 sec)

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