Question

Below is my query and its output. Is it possible to build my query with only one select statement (I have two in my query)? It’s for performance purposes.

WITH GradePassFail AS (
    SELECT 
        Subject, 
        Grade, 
        CASE WHEN Grade >= 50 THEN 1 ELSE 0 END AS Pass, 
        CASE WHEN Grade < 50 THEN 1 ELSE 0 END AS Fail 
    FROM Grade_report
)
SELECT Subject, MAX(Grade) AS Grade, SUM(Pass) AS Pass, SUM(Fail) AS Fail
FROM GradePassFail
GROUP BY Subject

Answer 1

You can perform the CASE statements for Pass/Fail within the SUM function… then you don’t need the CTE:

SELECT
    Subject,
    MAX(Grade) Grade,
    SUM(CASE WHEN Grade >= 50 THEN 1 ELSE 0 END) AS Pass,
    SUM(CASE WHEN Grade < 50 THEN 1 ELSE 0 END) AS Fail
FROM
    Grade_report
GROUP BY Subject

You can verify here:

http://sqlfiddle.com/#!3/99cd4/7