Question

我试图运行此查询：

  $sql = "SELECT p.*, c.id as cid, c.name as catname, p.title as ptitle,"
  . "\n CONCAT(u.first,' ',u.last) as user," 
  . "\n (SELECT GROUP_CONCAT(DISTINCT tags) as tagnames FROM tagtable WHERE id IN (p.tagids))" 
  . "\n FROM posts as p" 
  . "\n LEFT JOIN categories as c ON c.id = a.cid" 
  . "\n LEFT JOIN users as u ON u.id = a.uid" 
  . "\n WHERE a.active = 1 LIMIT 1";

我唯一的问题是使用子查询

"SELECT GROUP_CONCAT(DISTINCT tags)..."

由于某种原因，它不会产生任何结果。我希望将标签名称排为

＆＃34; lorem，ipsum，dolores，...＆＃34;

字段 tag-ids 采用1,2,3格式。

Answer 1

如果tagids的格式为'1,2,3'，请使用

FIND_IN_SET

如果字符串str在，则返回1到N范围内的值字符串列表strlist由N个子串组成。

所以，像

WHERE FIND_IN_SET(id,p.tagids) > 0

PHP和MySQL子查询，其中id为（）

1 个答案:

SQL Fiddle DEMO