如何在SQL LIKE查询中添加列值？

Question

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

但它给出以下错误：

错误1064：您的SQL语法有错误； 检查与您的MySQL服务器版本相对应的手册以获取正确的语法，以在第1行的'+ p.postid +'％'和e.params类似于'％parentid ='+ q.postid +'％'ORDER BY datetime DESC'处使用

似乎不喜欢+号，我认为这是在查询中添加值的正确方法。 我猜不:)我如何要求它检查一个表（一个整数）的列值是否在另一个表（一个字符串）的列值中？

编辑：感谢您的回答，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

Answer 1

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

Answer 2

请参阅MySQL文档中的CONCAT() ： http : //dev.mysql.com/doc/refman/5.1/en/string-functions.html#function_concat

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