phpPgAdmin的選擇（MAX（從（SELECT COUNT（*）爲num ... NUM））作爲計數）

Question

我試試這個：

SELECT x.name 
FROM s x 
WHERE (SELECT MAX(num) 
     FROM ((SELECT COUNT(*) AS num 
       FROM spj 
     WHERE n_post=x.n_post)>0) AS adf) 

錯誤消息：

ERROR: syntax error at or near ">

LINE 2: ...CT count(*) as num from spj where n_post=x.n_post)>0) as adf...

然後我試試這個：

SELECT x.name 
FROM s x 
WHERE (SELECT MAX(num) 
     FROM ((SELECT COUNT(*) AS num 
       FROM spj 
       WHERE n_post=x.n_post)) AS adf) 

錯誤消息：

ERROR: argument of WHERE must be type boolean, not type bigint LINE 2: where (select max(num) from ((SELECT count(*) as num from sp..

出了什麼問題？請幫幫我。

Thx。我的代碼：

SELECT x.name 
FROM s x 
WHERE (SELECT MAX(num) 
     FROM (SELECT COUNT(*) AS num 
       FROM spj 
     WHERE x.n_post=n_post) AS adf)>0 

我需要n_post，這在表SPJ的最大條目數，但我不知道該怎麼做。

Answer 1

如果您需要n_post，它具有表spj中的最大條目數嘗試使用此查詢。這是MySQL查詢，它使用LIMIT關鍵字。如果您使用MsSQL，則使用SELECT TOP 1而不是LIMIT 1。

SELECT x.name 
FROM s x 
JOIN (SELECT n_post,COUNT(*) AS num FROM spj GROUP BY n_post) as y 
    on x.n_post=y.n_post 
ORDER BY y.num DESC 
LIMIT 1