如何在SQL Server的"select"语句中获取表名

Question

我UNION或多或少要这样做:

select [table_name], name, address
from Employees
where [my_condition]

UNION

select [table_name], name, address
from Employees_history
where [my_condition]

检索到的数据将在Employees或Employees_history中,但不在两个表中.

我需要知道数据来自哪个表.

Answer 1

SELECT 'Employees' AS [table_name],
       name,
       address
FROM   Employees
WHERE  [my_condition]
UNION ALL
SELECT 'Employees_history' AS [table_name],
       name,
       address
FROM   Employees_history
WHERE  [my_condition] 

我使用UNION ALL而不是UNION因为两个分支中没有重复.因此,它可以避免一些不必要的工作,删除整个结果集中的重复项.

如果分支机构中可能存在重复项DISTINCT,则添加到个人SELECT(s)