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The COUNT() function returns the number of rows that matches
a specified criteria.
Syntax for SQL COUNT(column)
The COUNT(columnname) function returns the total number
of Record of the specified column.In this case the NULL values will not be
counted.
SELECT COUNT(columnname) FROM tablename
Syntax
for SQL SQL COUNT(*)
The COUNT(*) function returns the total number of records in the
specified table:
SELECT COUNT(*) FROM tablename
Syntax for
SQL COUNT(DISTINCT
columnname)
The COUNT(DISTINCT
columnname) function returns the number of distinct values of the specified
column in a table:
SELECT COUNT(DISTINCT columnname) FROM tablename
Example: We have the following
"Orders" table:
| O_Id | Date | Price | Customer_Name |
|---|---|---|---|
| 1 | 2012/11/12 | 10000 | Rajesh |
| 2 | 2012/10/23 | 16000 | Shiv |
| 3 | 2012/09/02 | 7000 | rupa |
| 4 | 2012/09/03 | 3000 | Hansen |
| 5 | 2012/08/30 | 20000 | Jensen |
| 6 | 2012/10/04 | 1000 | Shiv |
Here we want to count the number of orders from
'Customer Shiv' the sql statement we use looks like this .
SELECT COUNT(Customer_name) FROM Orders
WHERE Customer='Shiv'
Result :2
if we use this statement:
SELECT COUNT(*) FROM Orders
Result:6
