A couple of skills that I have used as a database developer

- Thinking of data in sets instead or rows. (this will avoid cursor processing)

- multi table updates and deletes

- Analytical functions

- Merge statement

Like others mentioned a basic understanding of SQL server 'under the hood' as far as DML is concerned like Indexes and such. (I may have steered away from the topic!)

My two cents, thanks for listening!

MM