CODEWITHSUNDEEP
mysql
Ram
Ram

Reputation: 387

select case with order by in mysql

I am running following query to find the best winning streak for user.

$sql="select sub.user_id as user_id,max(sub.streak) as streak,max(sub.units) as units
                from
                  (
                select 
                case when @x is null then @x:=user_id end,
                case 
                when awarded_unit>0 and @x=user_id then @y:=@y+1 
                when awarded_unit<0 and @x=user_id then @y:=0 
                when awarded_unit>0 and @x<>user_id then @y:=1
                when awarded_unit<0 and @x<>user_id then @y:=0
                end as streak,
                case 
                when awarded_unit>0 and @x=user_id then @z:=@z+awarded_unit 
                when awarded_unit<0 and @x=user_id then @z:=0 
                when awarded_unit>0 and @x<>user_id then @z:=awarded_unit 
                when awarded_unit<0 and @x<>user_id then @z:=0
                end as units,
                @x:=user_id as user_id,
                awarded_unit
                from $select_user_events_fights as u,$events as e,$event_fight_table as ef,$post_meta as pm where e.ID=ef.event_id
                and ef.event_fight_id=u.event_fight_id and  e.post_type='bt_events' and pm.post_id = e.ID and  e.post_status ='publish' and pm.meta_key='_event_dt_time' and u.`awarded_unit`!=0 and u.season_id=$season_id and u.user_id=".$user->ID."

                order by pm.meta_value desc,ef.fight_order desc
                  ) as sub
                group by sub.user_id";


            mysql_query("set @y=0;");
            mysql_query("set @x=null;");
            mysql_query("set @z=0;");

It works fine if I put order by u.primary_key. But I wants events to be sorted by date and fight order . it gives wrong result in this case.

I had checked inner query with order by statement.

for order by statement("order by pm.meta_value desc,ef.fight_order desc") ,it is sorting results after calculating the best streak so it is giving wrong result.

Kindly explain how to get correct answer and what I am missing here.Thanks

Upvotes: 0

Views: 267

Answers (1)

Barmar
Barmar

Reputation: 781058

You need to do the ORDER BY in a subquery, and then perform the streak detection in an outer query that processes that.

Try this (untested -- if you want me to test, supply some data in a sqlfiddle):

      $sql="select sub.user_id as user_id,max(sub.streak) as streak,max(sub.units) as units
            from
              (
            select 
            case when @x is null then @x:=user_id end,
            case 
            when awarded_unit>0 and @x=user_id then @y:=@y+1 
            when awarded_unit<0 and @x=user_id then @y:=0 
            when awarded_unit>0 and @x<>user_id then @y:=1
            when awarded_unit<0 and @x<>user_id then @y:=0
            end as streak,
            case 
            when awarded_unit>0 and @x=user_id then @z:=@z+awarded_unit 
            when awarded_unit<0 and @x=user_id then @z:=0 
            when awarded_unit>0 and @x<>user_id then @z:=awarded_unit 
            when awarded_unit<0 and @x<>user_id then @z:=0
            end as units,
            @x:=user_id as user_id,
            awarded_unit
            from (select user_id, awarded_unit
                  from $select_user_events_fights as u,$events as e,$event_fight_table as ef,$post_meta as pm where e.ID=ef.event_id
            and ef.event_fight_id=u.event_fight_id and  e.post_type='bt_events' and pm.post_id = e.ID and  e.post_status ='publish' and pm.meta_key='_event_dt_time' and u.`awarded_unit`!=0 and u.season_id=$season_id and u.user_id=".$user->ID."

                  order by pm.meta_value desc,ef.fight_order desc) as subsub
            ) as sub
            group by sub.user_id";

Upvotes: 1

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