mysql - 我如何在查询中实现预期输出

Question

在此查询中，仅显示一条记录，请帮助...

("SELECT p.project_name, p.category, p.status, count(b.developer_id) AS developer_id 
 FROM project p , bidding b 
 WHERE p.project_id=b.bid_id AND p.client_reg_id='"+LID+"'");

Answer 1

COUNT 是一个聚合函数，总是将多个寄存器分组到一个寄存器中。将其从查询中删除，您将看到所有行。更多信息http://dev.mysql.com/doc/refman/5.6/en/group-by-functions.html#function_count

("SELECT p.project_name, p.category, p.status, b.developer_id AS developer_id 
  FROM project p , bidding b 
  WHERE p.project_id=b.bid_id AND p.client_reg_id='"+LID+"'");

编辑

试试这个:

SELECT p.project_name, p.category, p.status, count(b.developer_id) AS developer_bid_count
FROM project p
INNER JOIN bidding b 
ON p.project_id = b.bid_id
WHERE p.client_reg_id='"+LID+"'
GROUP BY p.project_id

我假设 project_id 是您的 project 表中的主键。当我们指定group by字段时，如果该字段是主键，则查询将每个项目返回一行，计算每个开发者有多少个出价