来自不同表的SQL多连接引用表

I am working with MSSQL. As long as I have been working on a project with a customer who bought our software, we are at the final step. At that point we have to give them some SQL queries to get some reports from MSSQL database.

我正在使用MSSQL。只要我与购买我们软件的客户一起开展项目,我们就是最后一步。那时我们必须给他们一些SQL查询来从MSSQL数据库中获取一些报告。

As I am not a familiar with SQL I am having a problem with joining multiple tables.

由于我不熟悉SQL,因此加入多个表时遇到问题。

I have searched some and created a query but the problem is joining a table with others which has no common column with the table I noticed after FROM tag.

我搜索了一些并创建了一个查询,但问题是加入一个表与其他没有共同列的表与我在FROM标记后注意到的表。

Let me explain a little:

让我解释一下:

I have 5 tables "x", "y", "z", "w", "m".

我有5个表“x”,“y”,“z”,“w”,“m”。

"x" table have common columns with "y", "z" and "w" tables

“x”表具有带“y”,“z”和“w”表的公共列

"m" table has a common column with "y" table

“m”表有一个带有“y”表的公共列

I want to select one another column from "m" for my report how can I join "x" with that table,

我想从“m”中为我的报告选择另一列,如何将“x”与该表连接,

How can I do this?

我怎样才能做到这一点?

3 个解决方案

#1

You can join x to y, and then join the combination of x and y to m. You don't need to select any of the columns from y if you want your result to have only columns from x and m. Something like:

您可以将x连接到y,然后将x和y的组合连接到m。如果希望结果只包含x和m的列,则无需从y中选择任何列。就像是:

SELECT x.column_from_x, m.column_from_m
    FROM x
    JOIN y
    ON x.xy_common_column = y.xy_common_column
    JOIN m
    ON m.my_common_column = y.my_common_column

Any WHERE clause you might want can follow this. There's a more concrete example here: https://technet.microsoft.com/en-us/library/ms191430(v=sql.105).aspx

您可能想要的任何WHERE子句都可以遵循此。这里有一个更具体的例子:https://technet.microsoft.com/en-us/library/ms191430(v = sql.105).aspx

#2

This is, indeed, a very basic question, but here you go.

这确实是一个非常基本的问题,但是你走了。

SELECT * 
FROM X
    INNER JOIN Y ON X.XYColumn = Y.XYColumn
    INNER JOIN M ON M.YMColumn = Y.YMColumn

#3

Since M, Y and X have something in common, you can use the code below

由于M,Y和X有一些共同点,您可以使用下面的代码

SELECT
M.Col,
X,CoL
FROM M
INNER JOIN Y ON M.ID = Y.ID
INNER JOIN X ON Y.ID=X.ID

#1