左连接的正确语法

Question

有人能告诉我为什么这个sql查询不执行？

SELECT t_ads.*, t_adpics.picfile, 
FROM t_ads 
LEFT JOIN t_adpics ON t_ads.adid = t_adpics.adid AND t_adpics.isevent = '0' 
LEFT JOIN t_featured ON t_ads.adid = t_featured.adid AND t_featured.adtype = 'A' 
WHERE (a.adtitle LIKE '%findandpost%' OR a.addesc LIKE '%findandpost%') 
AND a.enabled = '1' 
AND a.verified = '1' 
AND a.expireson >= NOW() 
AND a.paid <> '0' 
AND (t_featured.adid IS NULL OR t_featured.featuredtill < NOW()) 
GROUP BY t_ads.adtitle 
ORDER BY RAND() LIMIT 0, 50 

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 'FROM t_ads LEFT JOIN t_adpics ON t_ads.adid = t_a' at line 4

Answer 1

与你陈述的问题是你有FROM子句前额外的逗号，

SELECT t_ads.*, t_adpics.picfile, FROM 
           ^remove this comma 

Answer 2

您需要删除,

变化

SELECT t_ads.*, t_adpics.picfile, FROM 

到

​​

Answer 3

你必须把情况和t_featured.adtype = 'A'在WHERE子句中，并删除,前FROM关键字

SELECT t_ads.*, t_adpics.picfile 
FROM t_ads LEFT JOIN t_adpics ON t_ads.adid = t_adpics.adid 
LEFT JOIN t_featured ON t_ads.adid = t_featured.adid 
WHERE (a.adtitle LIKE '%findandpost%' OR a.addesc LIKE '%findandpost%') 
     AND a.enabled = '1' AND a.verified = '1' 
     AND a.expireson >= NOW() AND a.paid <> '0' 
     AND (t_featured.adid IS NULL OR t_featured.featuredtill < NOW()) 
     AND t_featured.adtype = 'A' 
     AND t_adpics.isevent = '0' 
GROUP BY t_ads.adtitle ORDER BY RAND() LIMIT 0, 50