One of the SQL Master tables records multiple record statements corresponding to the schedule

One of the SQL Master tables records multiple record statements corresponding to the schedule

Like this, we use the

Union statement

SQL Union syntax

Select column_name (s) from table_name1
Union
Select COLUMN_NAME (s) from Table_name2

Join left statement

LEFT JOIN keyword syntax

Select column_name (s)
From table_name1
Left JOIN Table_name2
On Table_name1.column_name=table_name2.column_name

where child query

SELECT * from a b where a.id=b.id

Here, let's look at an example.

Select XXXX from main Table INNER join schedule on Main table. xxxx= schedule. xxxx where xxxx

Example Description.

Employees_china:
e_id E_name
Zhang, Hua
Wang, Wei
Carter, Thomas
Yang, Ming

Employees_usa:
e_id E_name
Adams, John
Bush, George
Carter, Thomas
Gates, Bill.

List all the different employee names in China and the United States:

Select E_name from Employees_china
Union
Select E_name from Employees_usa
Results
E_name
Zhang, Hua
Wang, Wei
Carter, Thomas.
Yang, Ming
Adams, John.
Bush, George.
Gates, Bill.