SQL query Beginner's Guide reading notes (v) Introduction to set operation and multi-table query

Part iii:thinking in Sets

CHAPTER7 Thinking in Sets

The three Mostcommon set operations is as follows.

• Intersection

• Difference

• Union

in the SQL The corresponding keywords in each of the

• Intersection

• Except

• Union

The actual database implementation generally supports the following corresponding database collection operations

• INNER JOIN

• OUTER JOIN

• UNION JOIN

But the difference is that the collection operation involves the values of all the columns in the table , and JOINs only refers to the column values specified in the table .

SQL query Beginner's Guide reading notes (v) Introduction to set operation and multi-table query