sql查询返回两个表之间的差异 [英] sql query to return differences between two tables

问题描述

我正在尝试比较两个表，SQL Server，以验证一些数据.我想从两个表中返回数据位于一个或另一个中的所有行.从本质上讲，我想展示所有的差异.为此，我需要检查三项数据，FirstName、LastName 和 Product.

I am trying to compare two tables, SQL Server, to verify some data. I want to return all the rows from both tables where data is either in one or the other. In essence, I want to show all the discrepancies. I need to check three pieces of data in doing so, FirstName, LastName and Product.

我对 SQL 还很陌生，而且我发现的很多解决方案似乎都使​​事情变得过于复杂.我不必担心 NULL.

I'm fairly new to SQL and it seems like a lot of the solutions I'm finding are over complicating things. I don't have to worry about NULLs.

我开始尝试这样的事情:

I started by trying something like this:

SELECT DISTINCT [First Name], [Last Name], [Product Name] FROM [Temp Test Data]
WHERE ([First Name] NOT IN (SELECT [First Name] 
FROM [Real Data]))

不过，我无法更进一步.

I'm having trouble taking this further though.

谢谢！

根据@treaschf 的回答，我一直在尝试使用以下查询的变体:

Based on the answer by @treaschf I have been trying to use a variation of the following query:

SELECT td.[First Name], td.[Last Name], td.[Product Name]
FROM [Temp Test Data] td FULL OUTER JOIN [Data] AS d 
ON td.[First Name] = d.[First Name] AND td.[Last Name] = d.[Last Name] 
WHERE (d.[First Name] = NULL) AND (d.[Last Name] = NULL)

但是当我知道 td 中至少有 1 行不在 d 中时，我一直得到 0 个结果.

But I keep getting 0 results back, when I know that there is at least 1 row in td that is not in d.

好的，我想我明白了.至少在我的几分钟测试中，它似乎工作得很好.

Ok, I think I figured it out. At least in my few minutes of testing it seems to work good enough.

SELECT [First Name], [Last Name]
FROM [Temp Test Data] AS td
WHERE (NOT EXISTS
        (SELECT [First Name], [Last Name]
         FROM [Data] AS d
         WHERE ([First Name] = td.[First Name]) OR ([Last Name] = td.[Last Name])))

这基本上是要告诉我什么是我的测试数据中不是的真实数据.这对于我需要做的事情来说完全没问题.

This is basically going to tell me what is in my test data that is not in my real data. Which is completely fine for what I need to do.

推荐答案

如果你有表 A 和 B，都带有 C，这里是记录，它们出现在表 A 中但不在 B 中:

IF you have tables A and B, both with colum C, here are the records, which are present in table A but not in B:

SELECT A.*
FROM A
    LEFT JOIN B ON (A.C = B.C)
WHERE B.C IS NULL

要通过单个查询获取所有差异，必须使用完整连接，如下所示:

To get all the differences with a single query, a full join must be used, like this:

SELECT A.*, B.*
FROM A
    FULL JOIN B ON (A.C = B.C)
WHERE A.C IS NULL OR B.C IS NULL

在这种情况下你需要知道的是，当一个记录可以在 A 中找到，但在 B 中找不到时，来自 的列>B 将为 NULL，对于那些出现在 B 而不是 A 中的列，来自 A 的列也是如此将为空.

What you need to know in this case is, that when a record can be found in A, but not in B, than the columns which come from B will be NULL, and similarly for those, which are present in B and not in A, the columns from A will be null.

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