将两个 table 与一个 table _name 列合并

Question

我想合并两个表（Student1，Student2）。

1 - 学生 1

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

2 - 学生 2

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

那么我想要这样的结果。

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    |

我只想使用 ANSI sql。

Answer 1

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

我假设你知道UNION和UNION ALL之间的区别，union带来独特的记录，它和UNION PERFORMED ON SETS一样，而union all会带来也有重复的行。

在您的情况下，由于第一列区分行，因此即使合并也会带来重复。

Answer 2

你可以使用

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

Answer 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

将两个 table 与一个 table _name 列合并

Union two tables with a table _name column

sql

ansi-sql