从table1，table2多列左连接

Question

我有两个表：table1，table2如下所示

table1:
id   name
1    tamil
2    english
3    maths
4    science

table2:
p1 p2 p3 p4 stat name
1  2  4  3   A   raja
2  3  4  1   A   maha

我的预期输出是

p1       p2       p3       p4
tamil   english   science  maths
english maths     science  tamil

可以帮助我找出确切的查询。应该使用左外连接。

Answer 1

SELECT t1.name AS p1, t2.name AS p2, t3.name AS p3, t4.name AS p4
FROM table2 tbl2 INNER JOIN table1 t1 ON tbl2.p1 = t1.id
INNER JOIN table1 t2 ON tbl2.p2 = t2.id
INNER JOIN table1 t3 ON tbl2.p3 = t3.id
INNER JOIN table1 t4 ON tbl2.p4 = t4.id

点击下面的链接查看正在运行的演示。

SQLFiddle

Answer 2

select P1, t1.Name,P2, t3.Name, P3,t4.Name, P4 , t5.Name From Table2 T2
left join table1  t1 on 
T2.P1 = T1.Id
left join  table1  t3 on 
T2.P2 = T3.Id
left join  table1  t4 on 
T2.P3 = T4.Id
 left join  table1  t5 on 
T2.P4 = T5.Id

Answer 3

从科目s，科目s1，科目s2，科目s3，time_t t中选择t.pr，s.name，s1.name，s2.name，s3.name，其中s.id = t.pr 和s1.id = t.p2和s2.id = t.p3和s3.id = t.p4;