How to Count Database Table Values With SQL COUNT

The query element, an important part of Structured Query Language, retrieves data based on specific criteria from a relational database. This retrieval is accomplished using the COUNT function, which—when paired with a particular column of the database—yields all sorts of information.

Northwind Database Example

The examples below are based on the commonly used Northwind database, which frequently ships with database products for use as a tutorial. Here's an excerpt from the database's Product table: 

Counting Records in a Table

The most basic query is counting the number of records in the table. To calculate the number of items in a product table, use the following query:

SELECT COUNT(*)
FROM product;

This query returns the number of rows in the table. It's seven, in this example.

Counting Unique Values in a Column

Use the COUNT function to identify the number of unique values in a column. In the example, to identify the number of different suppliers whose products appear in the produce department, execute the following query:

SELECT COUNT(DISTINCT SupplierID)
FROM product;

This query returns the number of distinct values found in the SupplierID column. In this case, the answer is three, representing rows 1, 2, and 3.

Counting Records Matching Criteria

Combine the COUNT function with the WHERE clause to identify the number of records that match certain criteria. For example, suppose the department manager wants to get a sense of the stock levels in the department. The following query identifies the number of rows representing UnitsInStock less than 50 units:

SELECT COUNT(*)
FROM product
WHERE UnitsInStock < 50;

In this case, the query returns a value of four, representing Chai, Chang, Aniseed Syrup, and Uncle Bob's Organic Dried Pears.

The COUNT clause is valuable to database administrators who seek to summarize data to meet business requirements. With a little creativity, you can use the COUNT function for a wide variety of purposes.