使用table _name列联合两个表

Question

我想结合两个表（Student1，Student2）。

1 - Student1

| student_code |  name   |  
--------------------------
| 1            |  katia  |   
| 2            |  roger  |   
| 3            |  ken    | 

2 - Student2

| student_code |  name   |  
--------------------------
| 3            |  katia  |   
| 4            |  roger  |   
| 5            |  ken    | 

然后我想得到这样的结果。

结果

|table_name| student_code |  name   |  
-------------------------------------
|Student1  | 1            |  katia  |   
|Student1  | 2            |  roger  |   
|Student1  | 3            |  ken    | 
|Student2  | 3            |  katia  |   
|Student2  | 4            |  roger  |   
|Student2  | 5            |  ken    | 

我想只使用ANSI sql。

Answer 1

您可以使用

SELECT 'Student1' AS table_name, student_code, name FROM Student1
UNION ALL
SELECT 'Student2' AS table_name, student_code, name FROM Student2

Answer 2

 select 'Student1' AS table_name,student_code,name from student1
 union
 select 'Student2' AS table_name,student_code,name from student2

我假设您知道UNION和UNION ALL之间的区别，union带来了唯一记录，它与UNION PERFORMED ON SETS相同，而union all会带来重复的行同样。

在你的情况下，由于第一列区分行，它甚至会带有重复项。

Answer 3

Use UNION ALL statement :

SELECT 'Student1' as table_name, student_code, name FROM Student1
UNION ALL 
SELECT 'Student2' as table_name, student_code, name FROM Student2