Using SQL COUNT

SQL COUNT: Main Tips

• This function returns the amount of rows that satisfy the defined criteria.
• COUNT(DISTINCT) is only supported by Microsoft SQL Server and ORACLE.

Syntax of SQL COUNT

COUNT(col_name)

Returns the amount of values (excluding NULL values) in the defined column:

SELECT COUNT(col_name) FROM tbl_name

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COUNT(*)

Returns the total amount of data records in the table:

SELECT COUNT(*) FROM tbl_name

COUNT(DISTINCT col_name)

Brings back the amount of values that are distinct (counting duplicate values as one value) from a defined column:

SELECT COUNT(DISTINCT col_name) FROM tbl_name

Demo Database

Below is a section of the customer_orders table – we'll use it as a demo database in our examples:

SQL COUNT Examples

COUNT(col_name)

In the code example below the statement calculated the amount of orders from a particular customer:

SELECT COUNT(ID) AS OrderFromCustomers FROM customer_orders WHERE customer_id = 2;

COUNT(*)

Here we calculate the full amount of orders:

SELECT COUNT(DISTINCT customer_id) AS NumberOfCustomer FROM customer_orders;

COUNT(DISTINCT col_name)

The following query will return the amount of unique customers:

SELECT COUNT(DISTINCT ID) AS NumberOfCustomer FROM Orders;