The Ultimate Guide to High Availability with MariaDB

COUNT

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Syntax

COUNT(expr)

Description

Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value.

COUNT(*) counts the total number of rows in a table.

COUNT() returns 0 if there were no matching rows.

From MariaDB 10.2.0, COUNT() can be used as a window function.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT COUNT(*) FROM student;
+----------+
| COUNT(*) |
+----------+
|        8 |
+----------+

COUNT(DISTINCT) example:

SELECT COUNT(DISTINCT (name)) FROM student;
+------------------------+
| COUNT(DISTINCT (name)) |
+------------------------+
|                      4 |
+------------------------+

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