我正在尝试使用MySQL执行以下查询：
SELECT e.event,
BINARY e.params as params,
UNIX_TIMESTAMP(e.datetime) AS datetime,
p.postid AS postid,
q.postid AS parentid
FROM qa_eventlog as e
LEFT JOIN qa_posts as p
LEFT JOIN qa_posts as q ON e.userid=1 AND
DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= datetime AND
e.params LIKE '%postid='+p.postid+'%' AND
e.params LIKE '%parentid='+q.postid+'%'
ORDER BY datetime DESC
但它给出了以下错误：
错误1064:您的SQL语法有错误；请查看与MySQL服务器版本对应的手册，以获得正确的语法在'+p.postid+'%'AND e.params LIKE'%parentid='+q.postid+'%'附近使用在第1行按日期时间DESC排序
它似乎不喜欢+符号，我认为这是在查询中添加值的正确方式；猜不到：）我该如何让它检查一个表（整数）的列值是否在另一个表的列值（字符串）中？
编辑：谢谢你的回答，这是使用CONCAT:的有效代码
SELECT e.event,
BINARY e.params as params,
UNIX_TIMESTAMP(e.datetime) AS datetime,
p.postid AS postid,
q.postid AS parentid
FROM qa_eventlog AS e
LEFT JOIN qa_posts AS p
ON e.params LIKE CONCAT('%postid=', p.postid, '%' )
LEFT JOIN qa_posts AS q
ON e.params LIKE CONCAT('%postid=', q.postid, '%' )
WHERE e.userid=1
AND DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= datetime
ORDER BY datetime DESC
试试这个，
SELECT e.event,
e.params as params,
UNIX_TIMESTAMP(e.datetime) AS datetime,
p.postid AS postid,
q.postid AS parentid
FROM qa_eventlog as e
LEFT JOIN qa_posts as p
ON e.id = p.id -- not sure on this. please supply
-- the correct linking columnID
LEFT JOIN qa_posts as q
ON e.id = q.id -- and this
WHERE (DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= datetime) AND
e.params LIKE CONCAT('%', 'postid=', p.postid, '%' ) AND
e.params LIKE CONCAT('%', 'parentid=', q.postid, '%' ) AND
e.userid = 1
ORDER BY datetime DESC
请参阅CONCAT()的MySQL文档：http://dev.mysql.com/doc/refman/5.1/en/string-functions.html#function_concat
例如：
SELECT e.event,
BINARY e.params as params,
UNIX_TIMESTAMP(e.datetime) AS datetime,
p.postid AS postid,
q.postid AS parentid
FROM qa_eventlog as e
LEFT JOIN qa_posts as p
LEFT JOIN qa_posts as q ON e.userid=1 AND
DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= datetime AND
e.params LIKE CONCAT('%postid=',p.postid,'%') AND
e.params LIKE CONCAT('%parentid=',q.postid,'%')
ORDER BY datetime DESC