Amazon Redshift will no longer support the creation of new Python UDFs starting Patch 198. Existing Python UDFs will continue to function until June 30, 2026. For more information, see the [ blog post ](https://amazonaws-china.com/blogs/big-data/amazon-redshift-python-user-defined-functions-will-reach-end-of-support-after-june-30-2026/). 

# STDDEV\$1SAMP and STDDEV\$1POP window functions
STDDEV\$1SAMP and STDDEV\$1POP

The STDDEV\$1SAMP and STDDEV\$1POP window functions return the sample and population standard deviation of a set of numeric values (integer, decimal, or floating-point). See also [STDDEV\$1SAMP and STDDEV\$1POP functions](r_STDDEV_functions.md).

STDDEV\$1SAMP and STDDEV are synonyms for the same function.

## Syntax
Syntax

```
STDDEV_SAMP | STDDEV | STDDEV_POP
( [ ALL ] expression ) OVER
(
[ PARTITION BY expr_list ]
[ ORDER BY order_list 
                        frame_clause ]
)
```

## Arguments
Arguments

 *expression *   
The target column or expression that the function operates on. 

ALL   
With the argument ALL, the function retains all duplicate values from the expression. ALL is the default. DISTINCT is not supported.

OVER   
Specifies the window clauses for the aggregation functions. The OVER clause distinguishes window aggregation functions from normal set aggregation functions.

PARTITION BY *expr\$1list*   
Defines the window for the function in terms of one or more expressions. 

ORDER BY *order\$1list*   
Sorts the rows within each partition. If no PARTITION BY is specified, ORDER BY uses the entire table.

 *frame\$1clause*   
If an ORDER BY clause is used for an aggregate function, an explicit frame clause is required. The frame clause refines the set of rows in a function's window, including or excluding sets of rows within the ordered result. The frame clause consists of the ROWS keyword and associated specifiers. See [Window function syntax summary](c_Window_functions.md#r_Window_function_synopsis).

## Data types
Data Types

The argument types supported by the STDDEV functions are SMALLINT, INTEGER, BIGINT, NUMERIC, DECIMAL, REAL, and DOUBLE PRECISION.

Regardless of the data type of the expression, the return type of a STDDEV function is a double precision number.

## Examples
Examples

The following example shows how to use STDDEV\$1POP and VAR\$1POP functions as window functions. The query computes the population variance and population standard deviation for PRICEPAID values in the SALES table. 

```
select salesid, dateid, pricepaid,
round(stddev_pop(pricepaid) over
(order by dateid, salesid rows unbounded preceding)) as stddevpop,
round(var_pop(pricepaid) over
(order by dateid, salesid rows unbounded preceding)) as varpop
from sales
order by 2,1;

salesid | dateid | pricepaid | stddevpop | varpop
--------+--------+-----------+-----------+---------
  33095 |   1827 |    234.00 |         0 |       0
  65082 |   1827 |    472.00 |       119 |   14161
  88268 |   1827 |    836.00 |       248 |   61283
  97197 |   1827 |    708.00 |       230 |   53019
 110328 |   1827 |    347.00 |       223 |   49845
 110917 |   1827 |    337.00 |       215 |   46159
 150314 |   1827 |    688.00 |       211 |   44414
 157751 |   1827 |   1730.00 |       447 |  199679
 165890 |   1827 |   4192.00 |      1185 | 1403323
...
```

The sample standard deviation and variance functions can be used in the same way.