Construct SQL query to find records that all have the same value

Question

I have a table related to reviews made by a person. The table has the following fields: reviewId , personId , isComplete , where isComplete is a boolean indicating whether the particular person completed his review.

Imagine the following values:

ReviewID | PersonID | isComplete |

   1         1         1
   2         1         1
   3         2         0
   4         2         0
   5         3         1
   6         3         0

In this case I should get only PersonID = 1 as a result because only they have completed all their reviews. I have tried many queries and the closest one was: SELECT * FROM reviews x WHERE 1 = ALL (SELECT isComplete FROM reviews y WHERE x.personid = y.personid AND isComplete=1);

Any suggestions or hints will be greatly appreciated.

Answer 1

• Table A contains all records
• Table B contains all people who have at least 1 outstanding review.
• We use a left join and eliminate nulls so that what remains is only users who have records with no outstanding reviews...

.

SELECT Distinct A.PersonID 
FROM TABLE A
LEFT JOIN Table B 
 on A.PersonID = B.PersonId
 and B.isComplete = 0
WHERE B.PersonId is null

I used distinct to only return 1 records.

Another way to do this (I believe to be the most efficient) would be to use an exists statement

SELECT Distinct A.PersonID
FROM table A
WHERE not exists (Select 1 from Table B where B.iscomplete=0 and A.PersonID=B.PersonID)

This basically says return all persons who don't have an incomplete review.

The premise in both these cases is that a single entry of an incomplete review is enough to exclude them from the result set.

Answer 2

SELECT DISTINCT(PersonID) FROM reviews 
WHERE PersonId NOT IN (
    SELECT DISTINCT(PersonID) FROM reviews WHERE isComplete = 0
)

Answer 3

There is more than one way to do this.

SELECT * FROM reviews a WHERE a.PersonId NOT IN
( SELECT b.PersonId FROM reviews b WHERE b.isComplete = 0 )

This is getting all the persons that match isComplete = 0 and then only including the persons that aren't in that list.