Question

我想结合两个查询的结果。我使用了select union但它强加了我的网站。（对于记录，我的php内存限制为128M）如何在不强加服务器的情况下组合这些查询的结果？

第一次查询

SELECT mybb_posts.pid, mybb_posts.dateline, mybb_posts.subject, mybb_users.username, mybb_users.avatar, mybb_posts.message
FROM mybb_posts, mybb_users
WHERE mybb_posts.uid = mybb_users.uid AND mybb_posts.fid <> 170 AND mybb_posts.fid <> 77 AND mybb_posts.fid <> 96
ORDER BY mybb_posts.dateline DESC

第二次查询

SELECT ek_yorumlar.id, ek_yorumlar.zaman, ek_yorumlar.icisim, mybb_users.username, mybb_users.avatar, ek_yorumlar.turu
FROM ek_yorumlar, mybb_users
WHERE ek_yorumlar.gonderen = mybb_users.uid
ORDER BY ek_yorumlar.zaman DESC

联盟查询

SELECT * FROM(  
SELECT mybb_posts.pid, mybb_posts.dateline, mybb_posts.subject, mybb_users.username, mybb_users.avatar, mybb_posts.message
FROM mybb_posts, mybb_users
WHERE mybb_posts.uid = mybb_users.uid AND mybb_posts.fid <> 170 AND mybb_posts.fid <> 77 AND mybb_posts.fid <> 96
ORDER BY mybb_posts.dateline DESC
) AS T  
UNION ALL
SELECT * FROM (  
SELECT ek_yorumlar.id, ek_yorumlar.zaman, ek_yorumlar.icisim, mybb_users.username, mybb_users.avatar, ek_yorumlar.turu
FROM ek_yorumlar, mybb_users
WHERE ek_yorumlar.gonderen = mybb_users.uid
ORDER BY ek_yorumlar.zaman DESC 
) AS T 
ORDER BY dateline DESC LIMIT 25

Answer 1

您正在达到内存限制，因为此查询会将符合条件的所有行添加到内存中，然后将其减少到25行。如果首先减少每个组件中的行，它应该通过仅先查看每个查询的一半然后再返回25行来减少内存负担，这样它才会考虑50行。

SELECT * FROM(  
SELECT mybb_posts.pid, mybb_posts.dateline, mybb_posts.subject, mybb_users.username, mybb_users.avatar, mybb_posts.message
FROM mybb_posts
inner join  mybb_users on mybb_posts.uid = mybb_users.uid 
WHERE mybb_posts.fid not in (170 ,77 ,96)
ORDER BY mybb_posts.dateline DESC LIMIT 25
) AS T  
UNION 
SELECT * FROM (  
SELECT ek_yorumlar.id, ek_yorumlar.zaman, ek_yorumlar.icisim, mybb_users.username, mybb_users.avatar, ek_yorumlar.turu
FROM ek_yorumlar
inner join  mybb_users on ek_yorumlar.gonderen = mybb_users.uid
ORDER BY ek_yorumlar.zaman DESC LIMIT 25
) AS T 
ORDER BY dateline DESC LIMIT 25

或者，您可以创建临时表，以减少在任何单个步骤中执行的计算量...

create temporary table firsthalf
 SELECT mybb_posts.pid, mybb_posts.dateline, mybb_posts.subject, mybb_users.username, mybb_users.avatar, mybb_posts.message
    FROM mybb_posts
    inner join  mybb_users on mybb_posts.uid = mybb_users.uid 
    WHERE mybb_posts.fid not in (170 ,77 ,96)
    ORDER BY mybb_posts.dateline DESC LIMIT 25;
create temporary table secondhalf
    SELECT ek_yorumlar.id, ek_yorumlar.zaman, ek_yorumlar.icisim, mybb_users.username, mybb_users.avatar, ek_yorumlar.turu
    FROM ek_yorumlar
    inner join  mybb_users on ek_yorumlar.gonderen = mybb_users.uid
    ORDER BY ek_yorumlar.zaman DESC LIMIT 25;

select * from firsthalf
union all 
select * from secondhalf
ORDER BY dateline DESC LIMIT 25

我如何结合这些SQL查询的结果？

1 个答案: