如果不存在并从数据库中获取正确的值

问题描述：

I am trying to insert list of items from dev.test1 table, but I am struggling with logic ...

Face following problems:

Before insert statements I would like to add "if not exists" - select content in dev.qa_postmetas
f.URL which I am getting in second query is not coming from correct row in dev.test1 - If want to select f.URL where f.title = b.title

Query:

INSERT INTO dev.qa_posts (type, categoryid, userid, created, title, content,          tags)
(SELECT  'Q_QUEUED', '1', '3', NOW(), f.title, f.img, f.tagsv
FROM dev.test1 f)
LIMIT 1;

INSERT INTO dev.qa_postmetas (postid, title, content) 
(select MAX(b.postid) , 'qa_q_extra',f.URL
from dev.qa_posts b
left JOIN dev.test1 as f on b.postid = f.id)
LIMIT 1 ;

Any assistance will be appreciated

我正在尝试从dev.test1表中插入项目列表，但我正在努力处理逻辑...

面对以下问题： p>

在插入语句之前我想添加“如果不存在” - 在dev.qa_postmetas中选择内容 li>

我在第二次查询中获得的f.URL不是来自dev.test1中的正确行 - 如果要选择f.URL，其中f.title = b.title li> \ n ul>

查询： p>

  INSERT INTO dev.qa_posts（type，categoryid，userid，created，title，content，tags）
  （SELECT'Q_QUEUED'，'1'，'3'，NOW（），f.title，f.img，f.tagsv 
FROM dev.test1 f）
LIMIT 1; 
 
INSERT INTO dev.qa_postmetas（postid  ，标题，内容）
（选择MAX（b.postid），'qa_q_extra'，f.URL 
从dev.qa_posts b 
left JOIN dev.test1 as f on b.postid = f.id）
LIMIT 1;  
  code>  pre> 
 
 欢迎任何帮助 p> 
  div>

答

To avoid emty records try IS NULL function in MySQL.

Second query you join to another one and limiting insertion to one. You may have more results from joined query then you attemt to insert.

Debug your second join select to check what results you have. Take out limitation to insert all records from joined queries.

Is that what you mean?

如果不存在并从数据库中获取正确的值

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