equivalent T-SQL Merge in Power Query

[renzhaj]

Hi guys,

with T-SQL Merge I can insert new data and update the existing in one statement. I guess I can split data and use the Power BI merge/append to achieve the same result in the end. But is there any easier way to make it?

Thanks

[dax]

Hi @renzhaj , 

I think this need to be based on your detailed requirement, so if possible,  could you please inform me more detailed information(such as your expected output and your sample data)? Then I will help you more correctly.

Please do mask sensitive data before uploading.

Thanks for your understanding and support.
Best Regards,
Zoe Zhi

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[renzhaj]

Thanks, Zoe.

It's a straightforward T-SQL Merge scenario. Query A is daily refreshed with new data(ID:4) and updated data(ID:1) only from the source system. Query B is not refreshed but updated by Query A and other queries every day.

Input:

Query A

ID	Colum_A
1	TTT
4	YYY

Query B

ID	Colum_A	Colum_B
1	AAA	1111
2	BBB	2222
3	CCC	3333

Output:

Query B

ID	Colum_A	Colum_B
1	TTT	1111
2	BBB	2222
3	CCC	3333
4	YYY	null

[dax · Accepted solution]

Hi @renzhaj , 

You could try below M code to see whether it work or not

let
    Source = Table.NestedJoin(#"Query B", {"ID"}, #"Query A", {"ID"}, "Query A", JoinKind.FullOuter),
    #"Expanded Query A" = Table.ExpandTableColumn(Source, "Query A", {"ID", "Colum_A"}, {"ID.1", "Colum_A.1"}),
    Custom1 = Table.ReplaceValue(#"Expanded Query A", each [ID.1], each if [ID.1]=null then [ID] else [ID.1], Replacer.ReplaceValue, {"ID.1"}),
    Custom2 = Table.ReplaceValue(Custom1, each [Colum_A.1], each if [Colum_A.1]=null then [Colum_A] else [Colum_A.1], Replacer.ReplaceValue, {"Colum_A.1"}),
    #"Removed Columns" = Table.RemoveColumns(Custom2,{"ID", "Colum_A"})
in
    #"Removed Columns"

Best Regards,
Zoe Zhi

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[artemus]

It would look something like:

Table.FromRecords(Table.TransformRows(Source, if <where clause> then _ & [ColumnA = ..., ColumnC = ...] else _))

Note performance might be bad. Also note that columns that are ommited are left unchanged. 

[Anonymous]

Hi @renzhaj,

Not as a standard function as far as I am aware. You can of course write you custom function to do this, and use it as a shortcut.

Kind regards,
JB