SQL Server: Count based on Condition

Many a times, you may want to do a count in SQL Server, based on a condition. The easiest way is to use a combination of SUM and CASE as shown in this example

Here’s the same query to try out

DECLARE @TT Table (
CourseID int, StudentID int, EnrolledBy varchar(25)
)

INSERT INTO @TT
SELECT 1, 1, 'Hrishi' UNION ALL
SELECT 1, 2, 'Sagar' UNION ALL
SELECT 1, 3, 'Tony' UNION ALL
SELECT 1, 2, 'James' UNION ALL
SELECT 1, 4, 'Krish' UNION ALL
SELECT 2, 5, 'Tony' UNION ALL
SELECT 2, 5, 'Molly' UNION ALL
SELECT 2, 6, 'Tony'

SELECT
COUNT(*) as 'Total Enrolled',
SUM(CASE
WHEN EnrolledBy = 'Tony'
THEN 1 ELSE 0 END) as 'EnrolledbyTony'
FROM
@TT

In the query shown above, we are using SUM and CASE to count data only for those records, which are Enrolled by Tony. Similarly instead of SUM, you can also use COUNT which only counts the non-null values.

OUTPUT