MySQL STD() function

Last update on March 02 2026 12:07:07 (UTC/GMT +8 hours)

STD() function

MySQL STD() function returns the population standard deviation of expression. The standard deviation is a statistical measure that quantifies the amount of variation or dispersion in a dataset.

It returns NULL if no matching row is found.

This function is useful in -

It gives you an idea of how much individual values deviate from the average.
A higher standard deviation indicates more spread-out data, while a lower standard deviation indicates more closely grouped data.
When analyzing data, the standard deviation helps you understand the distribution of values and identify potential outliers or anomalies.
In finance and risk analysis, standard deviation is used to measure the volatility or risk associated with investment returns or financial instruments.
In manufacturing or quality control processes, standard deviation helps assess the consistency of product specifications and identify variations that may require corrective actions.
Standard deviation is used to calculate confidence intervals, which provide a range within which a population parameter is likely to fall.
You can use standard deviation to compare the variability of different datasets and assess their similarity or difference.

Syntax:

STD(expr);

Where expr is an expression.

MySQL Version : 8.0

Example: MySQL STD() function

The following MySQL statement will return the population standard deviation of 'total_cost' from 'purchase' table.

Sample table: purchase

+------------+------------+----------------+------------+------------+---------+---------------------------------+----------+---------+-------------+-------------+------------+
| invoice_no | invoice_dt | ord_no         | ord_date   | receive_dt | book_id | book_name                       | pub_lang | cate_id | receive_qty | purch_price | total_cost |
+------------+------------+----------------+------------+------------+---------+---------------------------------+----------+---------+-------------+-------------+------------+
| INV0001    | 2008-07-15 | ORD/08-09/0001 | 2008-07-06 | 2008-07-19 | BK001   | Introduction to Electrodynamics | English  | CA001   |          15 |       75.00 |    1125.00 |
| INV0002    | 2008-08-25 | ORD/08-09/0002 | 2008-08-09 | 2008-08-28 | BK004   | Transfer  of Heat and Mass      | English  | CA002   |           8 |       55.00 |     440.00 |
| INV0003    | 2008-09-20 | ORD/08-09/0003 | 2008-09-15 | 2008-09-23 | BK005   | Conceptual Physics              | NULL     | CA001   |          20 |       20.00 |     400.00 |
| INV0004    | 2007-08-30 | ORD/07-08/0005 | 2007-08-22 | 2007-08-30 | BK004   | Transfer  of Heat and Mass      | English  | CA002   |          15 |       35.00 |     525.00 |
| INV0005    | 2007-07-28 | ORD/07-08/0004 | 2007-06-25 | 2007-07-30 | BK001   | Introduction to Electrodynamics | English  | CA001   |           8 |       25.00 |     200.00 |
| INV0006    | 2007-09-24 | ORD/07-08/0007 | 2007-09-20 | 2007-09-30 | BK003   | Guide to Networking             | Hindi    | CA003   |          20 |       45.00 |     900.00 |
+------------+------------+----------------+------------+------------+---------+---------------------------------+----------+---------+-------------+-------------+------------+

Code:


-- This query calculates the standard deviation of the 'total_cost' column in the 'purchase' table.
SELECT STD(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 STD(total_cost): This part of the query selects the standard deviation of the 'total_cost' column. Standard deviation is a 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 STD(total_cost)
    -> FROM purchase;
+-----------------+
| STD(total_cost) |
+-----------------+
|      315.392172 | 
+-----------------+
1 row in set (0.23 sec)

PREV : MIN()
NEXT : STDDEV_POP()