mysql - 在sql中加入四个以上的表

Question

我有以下包含以下列的表格:更多信息 http://sqlfiddle.com/#!2/8776a0/2

request : {id,request_id, client_id, product_name, designation_date_1, can }
assigned_samples:{id,labref, user_id, stat}
users{id, fname, lname}
clients:{id, name}
tracking_table{labref, activity, added_date}

我想做的是加入所有这些表并得出一个包含所有数据的大表与跟踪表连接时，条件是检查事件列是否已给定值，如“a”，如果未找到匹配行，则 date_added 应为 null 否则显示 date_added

result table {labref, prod, desc_date, can, CONCAT(fname,' ',lname), date_added}

SELECT r.request_id, r.product_name, r.can, r.designation_date_1, CONCAT(u.fname,' ', u.lname) as analyst, a_s.stat
FROM request r, assigned_samples a_s, user u, clients c
WHERE r.client_id=c.id
AND a_s.analyst_id = u.id
AND r.request_id = a_s.labref
AND r.client_id='2'
GROUP BY r.request_id

如果我在查询中添加条件，它会返回数据，但 date_added 完全相同，这是错误的

SELECT r.request_id, r.product_name, r.can, r.designation_date_1, CONCAT(u.fname,' ', u.lname) as analyst, a_s.stat
FROM request r, assigned_samples a_s, user u, clients c, tracking_table t
WHERE r.client_id=c.id
AND a_s.analyst_id = u.id
AND r.request_id = a_s.labref
AND t.activity ='Authorizing COA Release'
AND r.client_id='2'
GROUP BY r.request_id

Answer 1

应为tracking_table 添加

加入条件。

试试这个:

SQLFiddle: http://sqlfiddle.com/#!2/3a116f/1

(我稍微更改了演示的输入数据)

SELECT r.request_id, r.product_name, r.can, r.designation_date_1, CONCAT(u.fname,' ', u.lname) as analyst, a_s.stat,
  date_added
FROM request r, assigned_samples a_s, user u, clients c, tracking_table t
WHERE r.client_id=c.id
AND a_s.analyst_id = u.id
AND r.request_id = a_s.labref
AND r.client_id='2'
AND r.request_id = t.labref
AND t.activity ='Authorizing COA Release'