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Version: 2.5

multi_distinct_count

Description

Returns the total number of rows of the expr, equivalent to count(distinct expr).

Syntax

multi_distinct_count(expr)

Parameters

expr: the column or expression based on which multi_distinct_count() is performed. If expr is a column name, the column can be of any data type.

Return value

Returns a numeric value. If no rows can be found, 0 is returned. This function ignores NULL values.

Examples

Suppose there is a table named test. Query the category and supplier of each order by id.

select * from test order by id;
+------+----------+----------+------------+
| id | country | category | supplier |
+------+----------+----------+------------+
| 1001 | US | A | supplier_1 |
| 1002 | Thailand | A | supplier_2 |
| 1003 | Turkey | B | supplier_3 |
| 1004 | US | A | supplier_2 |
| 1005 | China | C | supplier_4 |
| 1006 | Japan | D | supplier_3 |
| 1007 | Japan | NULL | supplier_5 |
+------+----------+----------+------------+

Example 1: Count the number of distinct values in the category column.

select multi_distinct_count(category) from test;
+--------------------------------+
| multi_distinct_count(category) |
+--------------------------------+
| 4 |
+--------------------------------+

Example 2: Count the number of distinct values in the supplier column.

select multi_distinct_count(supplier) from test;
+--------------------------------+
| multi_distinct_count(supplier) |
+--------------------------------+
| 5 |
+--------------------------------+