从联合mysql查询获得帖子的数量？

Question

SELECT u.id  AS pid , 
     b2.id  AS id  , 
     b2.message AS MESSAGE, 
     b2.uid AS uid, 
     b2.date AS DATE 
FROM (
     (SELECT b.id   AS id  , 
       b.pid  AS pid , 
       b.message AS MESSAGE, 
       b.uid AS uid, 
       b.date  AS DATE 
     FROM  wall_posts AS b 
       JOIN Friends AS f 
       ON  f.id = b.pid 
     WHERE f.buddy_id = '1' 
     AND  f.status  = 'b' 
     ORDER BY DATE DESC 
     LIMIT 0, 10 
     ) 

UNION 
     (SELECT id  , 
        pid , 
        MESSAGE, 
        uid, 
        DATE 
     FROM  wall_posts 
     WHERE pid = '1' 
     ORDER BY DATE DESC 
     LIMIT 0, 10 
     ) 
     )   AS b2 
     JOIN Users AS u 
     ON  b2.pid = u.id 
WHERE u.banned   ='0' 
AND  u.email_activated='1' 
ORDER BY DATE DESC 
LIMIT 0, 10 

是代码。不知道我怎么会得到这个帖子。平时我知道我会做select count(*) as num我试图

所以我做了什么我把

SELECT u.id  AS pid , 
     b2.id  AS id  , 
     b2.message AS MESSAGE, 
     b2.uid AS uid, 
     b2.date AS DATE 
FROM 

，并把它改成

SELECT COUNT(u.id  AS pid , 
     b2.id  AS id  , 
     b2.message AS MESSAGE, 
     b2.uid AS uid, 
     b2.date AS DATE) as num 
FROM 

，并没有类似的东西所有的select语句，清楚，没有工作，不断得到错误，如#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AS pid , b2.id AS id , b2.message AS MESSAGE, b' at line 1。那么我怎么会得到伯爵呢？我需要计数我的分页php类。

Answer 1

php中的mysql_num_rows似乎将其关闭而不修改sql。

Answer 2

COUNT函数不允许您有多个列。它可以是COUNT（*）或COUNT（column_name），其中只有一个列名。 COUNT（*）格式计算总行数，其中COUNT（column_name）返回指定列的非空值的计数。

因此，下一步是在SELECT中改变COUNT。然后，如果存在其他问题，您可以从那里出发。