What core skills should someone have with T-SQL?

I'll start the list, but feel free to add to it or give me your thoughts. I think someone ought to be able to understand these items and write code to solve problems that involve:

finding duplicate rows (grouping, joins)
returning aggregates of single or multiple columns (MAX, MIN, SUM, COUNT)
return aggregates in groups, or islands. (grouping and aggregates, windowing)
join multiple tables together on matching, multiple columns (joins)
find data in one table that doesn't have matches in another (outer joins)
filtering data (WHERE) subqueries and complex CTE joins of data
create row numbers and join back to a table without numbers (APPLY)
pivoting data from rows to columns