Row number per group in mysql

Question

I want to produce query result base on this scenario that can create row number according to crew_id and type.

id   crew_id   amount    type
 1      4                


        

Answer 1

The question is quite old. But I would like to post it in case someone will have a same problem.

First of all, described answers do not work correct. For example, for

id   crew_id   amount    type
1      4       1000      AUB
2      4       1500      AUB
5      5       1000      AUB
6      6       3000      AUB
8      6       3500      AUB
9      4       5000      AUB

(I just removed rows with type 'CA') the result table will be

id   crew_id   amount    rank   type
1      4       1000      1      AUB
2      4       1500      2      AUB
9      4       5000      3      AUB
5      5       1000      4      AUB
6      6       3000      5      AUB
8      6       3500      6      AUB

So in fact it doesn't use both crew_id and type, it just uses type.

Here is how I solved this problem (probably there is a more elegant way to do it than use two nested 'CASE's, but you get the idea):

SELECT id,
    amount,
    CASE crew_id 
        WHEN @curCrewId THEN
            CASE type 
                WHEN @curType THEN @curRow := @curRow + 1 
                ELSE @curRow := 1
            END
        ELSE @curRow :=1
    END AS rank,
    @curCrewId := crew_id AS crew_id,
    @curType := type AS type
FROM Table1 p
JOIN (SELECT @curRow := 0, @curCrewId := 0, @curType := '') r
ORDER BY crew_id, type

The main idea remain. I just added a variable @curCrewId. If someone need to use 3 variables for grouping, so just use 3 variables and 3 nested 'CASE's. :)