Question

通过使用子查询库函数，如何选择与子查询中两个表的条件匹配的记录...？

这是实际的 sql查询

SELECT *, (SELECT count('report_id') 
           FROM report 
           WHERE report.category = category.cat_id 
                 and report.user_id IN (68, 69, 70)) AS cnt 
FROM (`category`)

我需要 codeigniter 中的等效项：

    $this->db->select('*')->from('category');
    $sub = $this->subquery->start_subquery('select');
    $sub->select("count('report_id')")->from('report')
        ->where_in(array('user_id'=>(68, 69, 70)));
    $this->subquery->end_subquery('number');

在这个我怎么能把我的第二个条件...... ???

Answer 1

顺便说一下，确实需要依赖子查询，这只会增加负载，并且会对类别表中的每一行执行，您可以将等效的连接查询写为

SELECT c.*, 
COUNT(DISTINCT r.report_id) AS cnt /*you can omit distinct if you have unique report ids  */
FROM `category` c
LEFT JOIN report r ON r.category = c.cat_id AND r.user_id IN (68, 69, 70)
GROUP BY c.cat_id

活动记录查询为

$result = $this->db->select('c.*,COUNT(DISTINCT r.report_id) AS cnt ',FALSE)
    ->from('category c')
    ->join('report r','r.category = c.cat_id AND r.user_id IN (68, 69, 70)','LEFT')
    ->group_by('c.cat_id')
    ->get()
    ->result();

子查询，其中条件来自codeigniter中的不同表

1 个答案: