Difference between union and union all in CDS views

[former_member482007]

Hi Team,

I have gone through some documents on Union and Union all in CDS views,I got to know that about union all but what is about union in CDS is there any example on Union.

Thanks

Murali

[enric101]

Hi,

According with this reference Abap CDS

• If the addition ALL is not specified, all duplicate entries are removed from the results set. They are not removed if ALL is specified

In this page have an example:

https://wiki.scn.sap.com/wiki/display/BI/Union+and+Union+All

Regards,

Enric

[former_member482007]

Right Answer

[gasparerdelyi]

Let me mention that even in the cases when results are the same there can be a difference in SQL elapsed times. When you have UNION the database is responsible for ensuring distinct results and pretty often it goes for a distinct operation.

Especially in cases when the developer knows that there is a field with a different value (or a field combination with always different value combinations) in the branches, UNION ALL can have much better performance.

[vvaree]

A union - It creates a union of rows in the results sets of 2 select statements. A union results set can itself be the left side of a further union. When using union , it removes the duplicates from the result set.

[former_member482007]

Yes,Right answer

[matt]

I'd hope it's right. It's the same answer given by Enric Castella Gonzalez two years ago...

[maheshpalavalli]

govindmurali,

Small Tip: instead of commenting that it is the correct answer, please click on the accept button on the answer and close the message.