Using a SELECT statement within a WHERE clause

Question

SELECT * FROM ScoresTable WHERE Score = 
  (SELECT MAX(Score) FROM ScoresTable AS st WHERE st.Date = ScoresTable.Date)

Is there a name to describe

Answer 1

It's not bad practice at all. They are usually referred as SUBQUERY, SUBSELECT or NESTED QUERY.

It's a relatively expensive operation, but it's quite common to encounter a lot of subqueries when dealing with databases since it's the only way to perform certain kind of operations on data.