VAR_SAMP¶

Syntax¶

Aggregate function

VAR_SAMP( [DISTINCT] <expr1> )

Window function

VAR_SAMP( <expr1> ) OVER (
                         [ PARTITION BY <expr2> ]
                         [ ORDER BY <expr3> [ ASC | DESC ] [ <window_frame> ] ]
                         )

For details about window_frame syntax, see Usage notes for window frames.

Arguments¶

expr1

The expr1 should evaluate to one of the numeric data types.

expr2

This is the expression to partition by.

expr3

This is the expression to order by within each partition.

Returns¶

The data type of the returned value is NUMBER(<precision>, <scale>). The scale depends upon the values being processed.

Usage notes¶

• For single-record inputs, VAR_SAMP, VARIANCE, and VARIANCE_SAMP all return NULL. This is different from the Oracle behavior, where VAR_SAMP returns NULL for a single record and VARIANCE returns 0.

• When passed a VARCHAR expression, this function implicitly casts the input to floating point values. If the cast cannot be performed, an error is returned.

• When called as a window function:

  • The keyword DISTINCT is permitted syntactically, but is ignored.

  • If an ORDER BY sub-clause is used inside the OVER clause, then a window frame must be used. If no window frame is specified, then the ORDER BY implies a cumulative window frame:

    RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW

    For more details about window frames, including syntax and examples, see Usage notes for window frames.

Examples¶

This example shows how to use the VAR_SAMP function:

Create and fill a table:

create table aggr(k int, v decimal(10,2), v2 decimal(10, 2));
insert into aggr values 
   (1, 10, null),
   (2, 10, 11), 
   (2, 20, 22), 
   (2, 25, null), 
   (2, 30, 35);

Copy

Query the table, calling VAR_SAMP():

SELECT k, var_samp(v), var_samp(v2) 
    FROM aggr 
    GROUP BY k
    ORDER BY k;
+---+---------------+----------------+
| K |   VAR_SAMP(V) |   VAR_SAMP(V2) |
|---+---------------+----------------|
| 1 |          NULL |           NULL |
| 2 | 72.9166666667 | 144.3333333333 |
+---+---------------+----------------+

Copy