Sql query not returning proper results

Question

im attempting to create a query that counts the occurrence of rows containing a certain steamid64 of the player from multiple tables. As of now, the query isn't returning the proper count. It seems that if the 'propsCount' is 2 and the 'killsCount' is 1 then the killsCount will be 2 for some reason. It seems like its matching the highest value in the row.

Here is the query:

SELECT users.steamid64, COUNT(props.steamid64) AS propsCount, COUNT(kills.steamid64) AS killsCount, COUNT(deaths.steamid64) AS deathsCount
FROM `sl_players` AS users
            LEFT JOIN `sl_deathLogs` AS deaths ON users.steamid64 = deaths.steamid64
            LEFT JOIN `sl_killLogs` AS kills ON users.steamid64 = kills.steamid64
            LEFT JOIN `sl_propLogs` AS props ON users.steamid64 = props.steamid64
        GROUP BY users.steamid64

Here is the returned data:

In the picture you can see the propsCount and the killsCount of the second player are both 2. The propsCount should be 1 and the killsCount is the proper value. Any ideas why the propsCount column is matching the killsCount column? This seems to occur when the column has at least a value of 1 and when another column has a greater value, it will match the greater value.

Answer 1

You should be aggregating before the JOIN . But if your matches for a given steamid64 are not too big and the tables have a unique id, then you can use the COUNT(DISTINCT) work-around:

SELECT p.steamid64,
       COUNT(DISTINCT pl.id) AS propsCount,
       COUNT(DISTINCT kl.id) AS killsCount,
       COUNT(DISTINCT dl.id) AS deathsCount
FROM sl_players p LEFT JOIN
     sl_deathLogs dl
     ON p.steamid64 = dl.steamid64 LEFT JOIN
     sl_killLogs kl
     ON p.steamid64 = kl.steamid64 LEFT JOIN
     sl_propLogs pl
     ON p.steamid64 = pl.steamid64
GROUP BY p.steamid64;

I don't know what the id is really called in the tables.

A more general solution is to aggregate before doing the JOIN or to use subqueries:

select p.steamid64,
       (select count(*) from sl_propLogs pl where p.steamid64 = pl.steamid64) as propsCount,
       (select count(*) from sl_killLogs kl where p.steamid64 = kl.steamid64) as killsCount,
       (select count(*) from sl_deathLogs dl where p.steamid64 = dl.steamid64) as deathsCount
from sl_players p;

This avoids the aggregation in the outer query. So, with appropriate indexes (on steamid64 in each of the log tables), it should be faster than the JOIN method.