Question

在下面的示例中，我将如何实现从不同表中选择的SQL查询。

SalesCodeA
----------------------------------------------------
ID | EMPLOYEE NAME | EMPLOYEE CODE || EMPLOYEE SALES
1     STEVE JOBS          A               1000

SalesCodeB
----------------------------------------------------
ID | EMPLOYEE NAME | EMPLOYEE CODE || EMPLOYEE SALES
1     BILL GATES          B               2000

SalesCodeC
----------------------------------------------------
ID | EMPLOYEE NAME | EMPLOYEE CODE || EMPLOYEE SALES
1     JOHN APPLE          C               3000

我将如何实现基于EmployeeCode获取数据的内容？我尝试使用

 SELECT * FROM SalesCodeA, SalesCodeB, SalesCodeC WHERE EmployeeCode ="A";

但它不起作用。

Answer 1

可能你正在寻找这个（UNION ALL）

SELECT ID,[EMPLOYEE NAME],[EMPLOYEE CODE],[EMPLOYEE SALES]
FROM   TABLE_1
WHERE  [EMPLOYEE CODE] = 'A'
UNION ALL
SELECT ID,[EMPLOYEE NAME],[EMPLOYEE CODE],[EMPLOYEE SALES]
FROM   TABLE_2
WHERE  [EMPLOYEE CODE] = 'A'
UNION ALL
SELECT ID,[EMPLOYEE NAME],[EMPLOYEE CODE],[EMPLOYEE SALES]
FROM   TABLE_3
WHERE  [EMPLOYEE CODE] = 'A'

同样为每位员工提供单独的表格看起来不是一个合适的设计，因为employee code或employee ID将是唯一的，因此为所有员工提供单一表格

Answer 2

我完全理解你的查询，但我可以建议你使用不同查询的联合，因为所有的表结构是相同的。

SELECT * FROM TABLE_1 WHERE EMP_CODE='A';
UNION
SELECT * FROM TABLE_2 WHERE EMP_CODE='B';
UNION
SELECT * FROM TABLE_3 WHERE EMP_COE='C';

Answer 3

试试这个：

SELECT * FROM (
SELECT * FROM SalesCodeA UNION ALL
SELECT * FROM SalesCodeB UNION ALL
SELECT * FROM SalesCodeC) t WHERE t.EmployeeCode ="A";

Answer 4

您可以使用UNION ALL运算符。确保所有表格具有相同的列数。

SELECT *
FROM
(SELECT * FROM SalesCodeA 
UNION ALL
SELECT * FROM SalesCodeB 
UNION ALL
SELECT * FROM SalesCodeC ) t
WHERE t.EMP_CODE='A';

如何从不同的表中选择值？

4 个答案: