mysql BLOB問題

Question

這工作正常。

SET @postrownum = 0, @postrank = 1, @postprev_val = NULL, @postprev_postnum = NULL; 

SELECT @postrownum := @postrownum + 1 AS row, 
@postrank := IF(@postprev_val!=postcount,@postrownum,@postrank) AS postrank, 
c.user_id, 
@postprev_postnum := IF(@postprev_val!=postcount,@postprev_val-postcount,@postprev_postnum) as morepost, 
@postprev_val := postcount as postcount, 
postcount*5 as postpoint from 

(
select user_id,count(user_id) as postcount from post group by user_id order by postcount desc) as c 

這並不做工精細

SET @postrownum = 0, @postrank = 1, @postprev_val = NULL, @postprev_postnum = NULL; 

select id,postrank,morepost,postcount,postpoint from user as a left join 

(SELECT @postrownum := @postrownum + 1 AS row, 
@postrank := IF(@postprev_val!=postcount,@postrownum,@postrank) AS postrank, 
c.user_id, 
@postprev_postnum := IF(@postprev_val!=postcount,@postprev_val-postcount,@postprev_postnum) as morepost, 
@postprev_val := postcount as postcount, 
postcount*5 as postpoint from 

(
select user_id,count(user_id) as postcount from post group by user_id order by postcount desc) as c) as b on a.id=b.user_id 

morepost將與[BLOB-1B]，怪異的回報。有人可以幫助！

Answer 1

很奇怪，問題在於此。

@postprev_postnum = NULL;

我設爲

@postprev_postnum = 0;

它適用於第二代碼。

不明白你爲什麼。