Unique results for SQL command with GROUP, MIN and NULL values

问题

I have a table inquiry with columns job, gender (TRUE for women, FALSE for men) and salary. None of the columns is unique, salary may contain NULL. How to find the minimum salary per job for women (TRUE)? If e.g. there are entries [pilot ; TRUE ; 100], [pilot ; FALSE ; 100], [pilot ; TRUE ; NULL] and [pilot ; FALSE ; 120], the code below returns [pilot ; 100] twice instead of once.

SELECT TOP (100) PERCENT T.JOB, T.SALARY
FROM INQUIRY AS T INNER JOIN
    (SELECT JOB, MIN(SALARY) AS SL
    FROM INQUIRY AS T
    WHERE (SALARY IS NOT NULL) AND (GENDER = 1)
    GROUP BY JOB) AS x ON x.JOB = T.JOB AND x.SL = T.SALARY

回答1:

Aggregate functions ignore nulls. Lose the join and you should be OK:

SELECT   job, MIN(salary)
FROM     inquiry
WHERE    gender = 1
GROUP BY job

来源：https://stackoverflow.com/questions/47352218/unique-results-for-sql-command-with-group-min-and-null-values