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Databases SQL Reporting by Example Day 3: Getting Good at Grouping Bus Troubles

György Varga
György Varga
19,198 Points

A more complex solution

Hi!

Please check out my solution. I've got the same teacher back. Is it good?

WITH ONEPERIODS AS (
SELECT PERIODS.ID AS "Periods ID" FROM PERIODS
LEFT JOIN CLASSES ON PERIODS.ID = CLASSES.PERIOD_ID
WHERE PERIODS.ID = 1
),

 FIRST_CLASS AS (
SELECT DISTINCT TEACHERS.ID AS "Teachers ID" FROM TEACHERS
LEFT JOIN CLASSES ON TEACHERS.ID = CLASSES.TEACHER_ID
LEFT JOIN ONEPERIODS ON CLASSES.PERIOD_ID = ONEPERIODS."Periods ID"
WHERE ONEPERIODS."Periods ID" IS NOT NULL
)

SELECT  TEACHERS.ID, TEACHERS.FIRST_NAME, TEACHERS.LAST_NAME FROM TEACHERS
LEFT JOIN FIRST_CLASS ON TEACHERS.ID = FIRST_CLASS."Teachers ID"
GROUP BY TEACHERS.ID
HAVING FIRST_CLASS."Teachers ID" IS NULL

Thank you!

1 Answer

It's wonderful György!