mysql-为什么这两个查询返回不同的结果

Question

For some reason these 2 mysql queries, which I thought were essentially the same thing with different formatting, are returning different results for the sum value, and I'm not entirely sure why.

query 1(returning correct value)

SELECT sum((getRankint(cs_times.mapid, 1123, 0, 0))) AS rankval
FROM cs_times
INNER JOIN cs_maps ON cs_times.mapid = cs_maps.mapid
WHERE stage =0
AND TYPE =0
AND active =1
AND playerid =1123
AND getRankint(
cs_times.mapid, 1123, 0, 0
) <11

query 2

SELECT @rankval := getRankint(cs_times.mapid, 1123, 0, 0) AS rankval, 
sum(@rankval)
FROM cs_times
INNER JOIN cs_maps ON cs_times.mapid = cs_maps.mapid
WHERE stage =0
AND TYPE =0
AND active =1
AND playerid =1123
AND getRankint(
cs_times.mapid, 1123, 0, 0
) < 11

If I compare the tables side by side without the sum function, they come out exactly the same. However the total sum value is coming out different. Any idea what could be causing this? Thanks.

(Also there's a redundant function call in the where section of the query, is there a way to clear that out so it's not calling the function twice?)

Answer 1

If I compare the tables side by side without the sum function, they come out exactly the same. However the total sum value is coming out different. Any idea what could be causing this?

It is because of combining the aggregate with row level column value.

There will be only one row result from your query.

• First value represents result of getRankint on first row column value fetched and
• the second represents sum of such ranks = count(*) * getRankit . Here the count value is the number of rows fetched that satisfies the where condition.