非常好的外国SQL教程！！强烈推荐 Introduction Week 1 at a Glance Day 1 Introduction to SQL Day 2 Introduction to the Query: The SELECT Statement Day 3 Expressions, Conditions, and Operators Day 4 Functions: Molding the Data You Retrieve Day 5 Clauses in SQL Day 6 Joining Tables Day 7 Subqueries: The Embedded SELECT Statement Week 1 in Review Week 2 at a Glance Day 8 Manipulating Data ....