What order should I merge and append queries in?

[Johnsnowlife]

I have multiple queries extracting client data out of excel tables. I eventually need to append all of them together. I also have a ClientNameMap table which maps different spellings of the name of the same person to their ClientID. 

Should I merge each initial table with the ClientNameMap to get the ClientID column and lose the ClientName column. and then append all the client tables? 

Or should I append all the client tables and then merge the final table with the ClientNameMap table to get the ClientID column and then lose the ClientName column? 

The first involves more steps, but would it be processed faster since I more rapidly get to the ClientID (integer)?

[v-shex-msft]

HI @Johnsnowlife,

>>Should I merge each initial table with the ClientNameMap to get the ClientID column and lose the ClientName column. and then append all the client tables? 

If these tables stored the similar structure records, you can merge them to one to help build relationships more easier.

I won't recommend you to merge all tables to append detail records to current table. These operations will generate huge amount of duplicate records.(may decrease the performance)

In my opinion, you can modify these tables and try to keep one entity one table.(e.g. customer table only store customer related info and the relationship column) Then use relationship column to build relationships link these tables.

Regards,

Xiaoxin Sheng