COUNT

Description

Aggregate function.

The COUNT() function calculates the number of records returned by a select query.

note

NULL values are not counted.

Syntax

  1. > COUNT(expr)

Arguments

ArgumentsDescription
exprAny expression.This may be a column name, the result of another function, or a math operation. * is also allowed, to indicate pure row counting.

Returned Value

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.

If there are no matching rows, COUNT() returns 0.

Examples

  1. > drop table if exists tbl1,tbl2;
  2. > create table tbl1 (col_1a tinyint, col_1b smallint, col_1c int, col_1d bigint, col_1e char(10) not null);
  3. > insert into tbl1 values (0,1,1,7,"a");
  4. > insert into tbl1 values (0,1,2,8,"b");
  5. > insert into tbl1 values (0,1,3,9,"c");
  6. > insert into tbl1 values (0,1,4,10,"D");
  7. > insert into tbl1 values (0,1,5,11,"a");
  8. > insert into tbl1 values (0,1,6,12,"c");
  10. > select count(col_1b) from tbl1;
  11. +---------------+
  12. | count(col_1b) |
  13. +---------------+
  14. |             6 |
  15. +---------------+
  17. > select count(*) from tbl1 where col_1d<10;
  18. +----------+
  19. | count(*) |
  20. +----------+
  21. |        3 |
  22. +----------+