MySQL STDDEV() function

Last update on May 01 2024 12:49:14 (UTC/GMT +8 hours)

STDDEV() function

MySQL STDDEV() function returns the population standard deviation of expression.

The STDDEV() function is used to calculate statistical information for a specified numeric field in a query. It returns NULL if no matching rows found.

This function is useful in -

It's used when you have a sample of data and want to estimate the variability in the entire population.
STDDEV() quantifies the spread or dispersion of values around the mean (average) in a sample.
When analyzing sample data, STDDEV() helps you assess the distribution of values and identify potential outliers or anomalies within the sample.
When comparing different samples or groups, STDDEV() is used to assess the significance of differences between the groups.
In some quality control processes, sample standard deviation helps assess the variability in products or processes.
Sample standard deviation is used to calculate confidence intervals for population parameters based on sample data.

Syntax:

STDDEV(expr);

Where expr is an expression.

MySQL Version: 8.0

Example: MySQL STDDEV() function

The following MySQL statement returns the standard deviation of 'total_cost' from purchase table.

Sample table: purchase

Code:


-- This query calculates the standard deviation of the 'total_cost' column in the 'purchase' table.
SELECT STDDEV(total_cost)             
-- This statement selects the standard deviation 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 standard deviation of the 'total_cost' values in the 'purchase' table.

SELECT STDDEV(total_cost): This part of the query selects the standard deviation of the 'total_cost' column. Standard deviation is a statistical measure of the amount of variation or dispersion in a set of values.

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 standard deviation of the 'total_cost' values in the 'purchase' table. This value provides insight into the spread or dispersion of the 'total_cost' values in the dataset.

Output:

mysql> SELECT STDDEV(total_cost)             
    -> FROM purchase;
+--------------------+
| STDDEV(total_cost) |
+--------------------+
|         315.392172 | 
+--------------------+
1 row in set (0.00 sec)

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