MYSQL：基于IF更新多个列

Question

Good morning, I tell them my situation: I have two tables:

RATINGS:
GUIDE   varchar(7)
USER    varchar(20)
PRETEST decimal(4,3)
POSTEST decimal(4,3)

RATINGS_PERGUIDE:
USER    varchar(20)
GUIDE1_PRETEST  decimal(4,3)
GUIDE1_POSTEST  decimal(4,3)
GUIDE2_PRETEST  decimal(4,3)
GUIDE2_POSTEST  decimal(4,3)3
.
.
.
GUIDE20_PRETEST decimal(4,3)
GUIDE20_POSTEST decimal(4,3)

Table "RATINGS" has a form for entering the information, I need to move the information entered to the table "RATINGS_PERGUIDE", i try this:

UPDATE RATINGS , RATINGS_PERGUIDE
IF RATINGS.USER = RATINGS_PERGUIDE.USER AND RATINGS.GUIDE = 'GUIDE 1'
THEN 
SET RATINGS_PERGUIDE.GUIDE1_PRETEST = RATINGS.PRETEST
SET RATINGS_PERGUIDE.GUIDE1_POSTEST = RATINGS.POSTEST
ELSE IF RATINGS.USER = RATINGS_PERGUIDE.USER AND RATINGS.GUIDE = 'GUIDE 2'
THEN 
SET RATINGS_PERGUIDE.GUIDE2_PRETEST = RATINGS.PRETEST;
SET RATINGS_PERGUIDE.GUIDE2_POSTEST = RATINGS.POSTEST;
.
.
.
END IF

But doesn't work

ie, according to the "GUIDE" entered in the table "RATINGS" update the corresponding column in the table "RATINGS_PERGUIDE" (24 "GUIDES" different)

Likewise, if it can be done in a trigger for each new record inserted into the table "RATINGS" would be much better

Please Help

Answer 1

You are trying to do a pivot in an update and that is a little complicated. One way is to simply do multiple updates:

update RATINGS_PERGUIDE join
       RATINGS
       on RATINGS.USER = RATINGS_PERGUIDE.USER and
          RATINGS.GUIDE = 'GUIDE 1'
    SET RATINGS_PERGUIDE.GUIDE1_PRETEST = RATINGS.PRETEST,
        RATINGS_PERGUIDE.GUIDE1_POSTEST = RATINGS.POSTEST;

Modify and repeat this update for each of the guides.

If you really want to do this in a single query:

update RATINGS_PERGUIDE join
       (select r.user,
               max(case when r.GUIDE = 'GUIDE 1' then pretest end) as pretest_guide1,
               max(case when r.GUIDE = 'GUIDE 1' then posttest end) as posttest_guide1,
               max(case when r.GUIDE = 'GUIDE 2' then pretest end) as pretest_guide2,
               max(case when r.GUIDE = 'GUIDE 2' then posttest end) as posttest_guide2,
               . . .
        from RATINGS r
        group by r.user
       ) r
       on r.USER = RATINGS_PERGUIDE.USER
    SET RATINGS_PERGUIDE.GUIDE1_PRETEST = r.pretest_guide1,
        RATINGS_PERGUIDE.GUIDE1_POSTEST = r.posttest_guide1,
        RATINGS_PERGUIDE.GUIDE2_PRETEST = r.pretest_guide2,
        RATINGS_PERGUIDE.GUIDE2_POSTEST = r.posttest_guide2,
        . . .

Answer 2

I have found the solution by simply observing the structure of "Update" in Phpmyadmin

UPDATE RATINGS , RATINGS_PERGUIDE
SET RATINGS_PERGUIDE.GUIDE1_PRETEST = (CASE WHEN RATINGS.GUIDE = 'GUIDE 1' THEN RATINGS.PRETEST ELSE RATINGS_PERGUIDE.GUIDE1_PRETEST END),
RATINGS_PERGUIDE.GUIDE1_POSTEST = (CASE WHEN RATINGS.GUIDE = 'GUIDE 1' THEN RATINGS.PRETEST ELSE RATINGS_PERGUIDE.GUIDE1_POSTEST END),
RATINGS_PERGUIDE.GUIDE2_PRETEST = (CASE WHEN RATINGS.GUIDE = 'GUIDE 2' THEN RATINGS.PRETEST ELSE RATINGS_PERGUIDE.GUIDE2_PRETEST END),
RATINGS_PERGUIDE.GUIDE2_POSTEST = (CASE WHEN RATINGS.GUIDE = 'GUIDE 2' THEN RATINGS.PRETEST ELSE RATINGS_PERGUIDE.GUIDE2_POSTEST END),
. . . .
WHERE RATINGS.USER = RATINGS_PERGUIDE.USER

And this work for me, I put it in a stored procedure and then call with a trigger

Thanks to All and to Gordon Linoff