1. Subqueries
- so far all joins are additive joins
- 2 joins will cover use a right table to determine which records to keep in the left table(오른쪽 표를 이용해서 왼쪽 표에 남겨둘 데이터를 결정)
- use a way similar to a WHERE clause
| Subqueries | DESCRIPTION |
|---|---|
SEMI JOIN | Matches records by key field in the right table with those in the left Then picks out only the rows in the left table that match that condition |
ANTI JOIN | Picks out those columns in the left table that do not match the condition on the right table |
 |
|---|
| SEMI JOIN & ANTI JOIN |
:)