Complex Queries,Triggers, Views, and Schema Modification
7.1. Describe the six clauses in the syntax of an SQL retrieval query. Show what type of constructs can be specified in each of the six clauses. Which of the six clauses are required and which are optional?
7.2. Describe conceptually how an SQL retrieval query will be executed by specifying the conceptual order of executing each of the six clauses.
7.3. Discuss how NULLs are treated in comparison operators in SQL. How are NULLs treated when aggregate functions are applied in an SQL query? How are NULLs treated if they exist in grouping attributes?
7.4. Discuss how each of the following constructs is used in SQL, and discuss the various options for each construct. Specify what each construct is useful for.
- Nested queries
- Joined tables and outer joins
- Aggregate functions and grouping
- Triggers
- Assertions and how they differ from triggers
- The SQL WITH clause
- SQL CASE construct
- Views and their up datability
- Schema change commands
