php - MySQL 中的 If 或 CASE 语句

Question

我正在尝试在 mqsql 中使用 if 或 case 语句...这是我的查询

$db->query("SELECT 
keywords.keyword,
keywords.keyid,
sources.s_title,
sources.s_disc,
sources.sourceid,
sources.s_link
FROM link_ks
INNER JOIN keywords ON link_ks.keyid = keywords.keyid
INNER JOIN sources ON link_ks.sourceid = sources.sourceid
case when 
thumbsup_items.votes_up+thumbsup_items.votes_down != ''
then 
INNER JOIN thumbsup_items ON link_ks.sourceid = thumbsup_items.name
 else null
WHERE link_ks.keyid = :keyid
 order by 
if((thumbsup_items.votes_up+thumbsup_items.votes_down) != '',
((thumbsup_items.votes_up+thumbsup_items.votes_down) desc ,thumbsup_items.votes_up desc,sources.sourceid),
sources.sourceid )
");

我已经使用了 CASE 并且 if Both 都是这个查询，但没有任何效果我知道 CASE 和 IF 都给出错误，但我不知道如何解决这个问题...

错误

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax

编辑 我的问题是这样的。如果没有投票，此查询不会给出任何输出，因此我使用 IF 语句

$db->query("SELECT 
keywords.keyword,
keywords.keyid,
sources.s_title,
sources.s_disc,
sources.sourceid,
sources.s_link
FROM link_ks
INNER JOIN keywords ON link_ks.keyid = keywords.keyid
INNER JOIN sources ON link_ks.sourceid = sources.sourceid
LEFT JOIN thumbsup_items ON thumbsup_items.votes_up+thumbsup_items.votes_down != '' AND link_ks.sourceid = thumbsup_items.name
WHERE link_ks.keyid = :keyid 
if((thumbsup_items.votes_up+thumbsup_items.votes_down) != '',
(thumbsup_items.votes_up+thumbsup_items.votes_down) desc ,
sources.sourceid )
");

现在 If 语句出错...请帮忙

Answer 1

将大小写移动到连接条件内，尝试以下操作:

SELECT 
keywords.keyword,
keywords.keyid,
sources.s_title,
sources.s_disc,
sources.sourceid,
sources.s_link
FROM link_ks
INNER JOIN keywords ON link_ks.keyid = keywords.keyid
INNER JOIN sources ON link_ks.sourceid = sources.sourceid
LEFT JOIN thumbsup_items ON thumbsup_items.votes_up+thumbsup_items.votes_down != '' AND link_ks.sourceid = thumbsup_items.name
WHERE link_ks.keyid = :keyid
ORDER BY 
CASE
    WHEN (thumbsup_items.votes_up+thumbsup_items.votes_down) != ''
    THEN (thumbsup_items.votes_up+thumbsup_items.votes_down)
    ELSE sources.sourceid
END DESC