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Inner Join, Left Outer Join and Association what is the difference, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain for you in detail, people with this need can come to learn, I hope you can gain something.

For the source code of the CDS view for testing, line 8 connects TJ02T with Inner Join, which stores the ID and description of all system states.

Inner Join test results: for states that do not maintain description information in TJ02T, they do not appear in the result set.

Change the Inner Join in the eighth row to Outer Join, and the test result is the opposite: notice that the row item with the value of E0001 in the stat column in the following figure also appears in the result set.

The test results of Association are consistent with those of Left Outer Join.

The underlying implementation of Association is actually the same as Left Outer Join. There are two ways to verify this conclusion.

Method 1

Preview a CDS view with an association implementation in ABAP Development Studio, and you can find that the association is finally implemented through Left Outer Join in the tool.

Method 2

This button in the transaction code ST05: displays the execution plan, and also shows that the underlying association is implemented by Left Outer Join.

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