CODEWITHSUNDEEP
mysql
Nightwhistle
Nightwhistle

Reputation: 198

Update one table if condition is met in another

I am wondering if this is possible to do in a single query (I'm trying to write one for quite some time now and nothing comes to my mind)

I have two tables:

tickets

+----------+-----+-----------+
| ticketid | win | processed |
+----------+-----+-----------+
|        1 |   0 |         0 |
|        2 |   0 |         0 |
|        3 |   0 |         0 |
+----------+-----+-----------+

playedmatches

+---------+----------+-----+-----------+
| matchid | ticketid | win | processed |
+---------+----------+-----+-----------+
|    1233 |        1 |   1 |         1 |
|    3144 |        1 |   0 |         1 |
|    1334 |        2 |   1 |         1 |
|    4441 |        2 |   1 |         1 |
|    1442 |        3 |   0 |         0 |
|    9723 |        3 |   1 |         1 |
+---------+----------+-----+-----------+

What I need is to update tickets.win and tickets.processed under rule that all rows in playedmatches of the given playedmatches.ticketid are processed. If lets say, every match with ticketid = 2 is processed = 1 I need to update tickets.processed to 1. Further, if all processed matches are win = 1 then tickets.win = 1 as well.

In this case, tickets table should like like: 

+----------+-----+-----------+
| ticketid | win | processed |
+----------+-----+-----------+
|        1 |   0 |         1 |
|        2 |   1 |         1 |
|        3 |   0 |         0 |
+----------+-----+-----------+

I have some ideas how to do this with 2 MySQL calls in php but I'm really trying to figure out if it is possible to do with just a single query.

Upvotes: 0

Views: 89

Answers (2)

Roland
Roland

Reputation: 976

You could make a view of playedmatches and aggregate over ticketid with 

count(ticketid) as a, sum(win) as b, sum(processed) as c

All tickets are processed when a = b. All processed matches are win when a = b = c.

This will give you the information you need to do the two updates via PHP.

Upvotes: 0

Oleg Komarov
Oleg Komarov

Reputation: 370

If you really want to have it in a single query, you can test something like this:

update tickets t join (
    select ticketid, if(sum(win) = count(*), 1, 0) as allwin
    from playedmatches
    group by ticketid
    having sum(processed) = count(*)
) j on j.ticketid = t.ticketid
set t.processed = 1,
    t.win = if(j.allwin, 1, t.win);

Upvotes: 2

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