SKEW,SKEW_POP,SKEWNESS
Description
Returns the skewness (opens in a new tab) of the expr expression.
The forumula used for this function is 3-th centrol moment / ((variance)^{1.5}), when variance is zero, SKEWNESS will return NULL.
Related Commands
Alias
- SKEW
- SKEW_POP
Syntax
SKEWNESS(<col>)Parameters
| Parameter | Description |
|---|---|
<col> | The column to be calculated skewness |
Return Value
Returns the skewness of the expr expression, which is a Double type.
Examples
CREATE TABLE statistic_test(
tag int,
val1 double not null,
val2 double null
) DISTRIBUTED BY HASH(tag)
PROPERTIES (
"replication_num"="1"
);
INSERT INTO statistic_test VALUES
(1, -10, -10),
(2, -20, NULL),
(3, 100, NULL),
(4, 100, NULL),
(5, 1000,1000);
-- NULL is ignored
SELECT
skew(val1),
skew(val2)
FROM statistic_test;+--------------------+------------+
| skew(val1) | skew(val2) |
+--------------------+------------+
| 1.4337199628825619 | 0 |
+--------------------+------------+-- Each group just has one row, result is NULL
SELECT
skew(val1),
skew(val2)
FROM statistic_test
GROUP BY tag;+------------+------------+
| skew(val1) | skew(val2) |
+------------+------------+
| NULL | NULL |
| NULL | NULL |
| NULL | NULL |
| NULL | NULL |
| NULL | NULL |
+------------+------------+