MEDIAN¶

Syntax¶

Aggregate function

MEDIAN( <expr> )

Window function

MEDIAN( <expr> ) OVER ( [ PARTITION BY <expr2> ] )

Argument¶

expr

The expression must evaluate to a numeric data type (INTEGER, FLOAT, DECIMAL, or equivalent).

Returns¶

Returns a FLOAT or DECIMAL (fixed-point) number, depending upon the input.

Usage notes¶

• If the number of non-NULL values is an odd number greater than or equal to 1, this returns the median (“center”) value of the non-NULL values.

• If the number of non-NULL values is an even number, this returns a value equal to the average of the two center values. For example, if the values are 1, 3, 5, and 20, then this returns 4 (the average of 3 and 5).

• If all values are NULL, this returns NULL.

• If the number of non-NULL values is 0, this returns NULL.

• DISTINCT is not supported for this function.

• When this function is called as a window function, it does not support:

  • An ORDER BY clause within the OVER clause.

  • Explicit window frames.

Examples¶

This shows how to use the function.

Create an empty table.

CREATE OR REPLACE TABLE aggr (k INT, v DECIMAL(10,2));

Get the MEDIAN value for column v. The function returns NULL because there are no rows.

SELECT MEDIAN(v)
  FROM aggr;

+------------+
| MEDIAN (V) |
|------------|
|       NULL |
+------------+

Insert some rows:

INSERT INTO aggr VALUES (1, 10), (1, 20), (1, 21);
INSERT INTO aggr VALUES (2, 10), (2, 20), (2, 25), (2, 30);
INSERT INTO aggr VALUES (3, NULL);

Get the MEDIAN value for each group. Note that because the number of values in group k = 2 is an even number, the returned value for that group is the mid-point between the two middle numbers.

SELECT k, MEDIAN(v)
  FROM aggr
  GROUP BY k
  ORDER BY k;

+---+-----------+
| K | MEDIAN(V) |
|---+-----------|
| 1 |  20.00000 |
| 2 |  22.50000 |
| 3 |      NULL |
+---+-----------+