从2个Tbal中选择SQL [英] SQL Selection from 2 Tbales

问题描述

大家好，

我有2个表Table1和Table2.
表1具有(A，B，C)列.表2具有(A，B，D).
表1具有52个Rceords.
表2有5条记录.表1中存在这5条记录.

现在我要从两个表中选择A，B，C，D.对于不存在的值，应显示为null.

例子:

A B C D
1 10空25
2 10 85空.

请帮助我.

问候，
Prasad

Hi All,

I have 2 tables Table1 and Table2.
Table1 have (A,B,C) columns. Table2 have (A,B,D).
Table1 Having 52 Rceords.
Table2 Having 5 records. These 5 are records are exist in Table1.

Now i want to select A,B,C,D from both tables. for non existing values it should show null.

example :

A B C D
1 10 null 25
2 10 85 null.

Please help me on this.

Regards,
Prasad

推荐答案

您好，我想下面的代码应该可以满足您的要求.

Hi, at a guess I believe the code below should do what you require.

SELECT
    t1.A
   ,t1.B
   ,t1.C
   ,t2.D
FROM
   Table1 t1
   LEFT OUTER JOIN Table2 t2 ON
      t1.A = t2.A AND
      t1.B = t2.B

我通常在表上使用左外连接"，我希望从
中得到空值
因此，猜测除了5个结果外，所有D都将为NULL.

希望对您有帮助

I usually use a Left Outer Join onto the table I want a null to come from

So at a guess you will have NULL in D for all but 5 results.

Hope that helps

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