如何从SQL中的两个不同表中选择值

Question

我的SQL Server数据库中有两个表.第一个是Test1第二个是Test2.RegNo两个表中都有一列.

现在我想从两个表中选择特定值RegNo.

这就是我正在做的事情

SELECT Test1.SurName, Test2.Class, Test2.Medium
FROM Test1,Test2 JOINS
Test2 ON Test1.RegNo = Test2.RegNo

但我的查询是错误的.

Answer 1

select
    Test1.SurName,
    Test2.Class,
    Test2.Medium
from Test1
inner join Test2
on Test1.RegNo = Test2.RegNo

如果要为特定数据选择数据RegNo,只需WHERE在末尾添加一个子句,如下所示:

select
    Test1.SurName,
    Test2.Class,
    Test2.Medium
from Test1
inner join Test2
on Test1.RegNo = Test2.RegNo
where Test1.RegNo = 123456   -- or whatever value/datatype your RegNo is

Answer 2

SELECT Test1.SurName, Test2.Class, Test2.Medium
FROM Test1 
INNER JOIN Test2 ON Test1.RegNo = Test2.RegNo