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Questions and Answers
What is the purpose of CREATE ASSERTION in SQL?
What components make up a typical trigger in SQL?
What is the concept of a view in SQL?
When would you use CREATE TRIGGER statement in SQL?
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What kind of constraints does CREATE ASSERTION in SQL deal with?
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In SQL, what is the purpose of a CREATE VIEW command?
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What is the responsibility of keeping a View up-to-date in SQL?
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Which strategy involves computing the view as and when needed without storing it permanently?
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What is a disadvantage of the query modification approach for implementing views?
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Which strategy involves physically creating a temporary view table when the view is first queried?
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What does the WITH CHECK OPTION clause do in SQL views?
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In which scenario is update not permitted on aggregate views in SQL?
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Study Notes
Triggers and Views in SQL
- The purpose of CREATE ASSERTION in SQL is to specify a constraint that must always be true.
- A typical trigger in SQL consists of three components: an event, a condition, and an action.
Views in SQL
- A view is a virtual table that is based on the result of an SQL statement, and its contents are derived from the data in one or more tables.
- The purpose of a CREATE VIEW command in SQL is to define a view, which is a virtual table based on the result of an SQL statement.
Creating Triggers
- The CREATE TRIGGER statement is used in SQL to define a trigger, which is a set of actions that are executed automatically in response to a specific event.
- Triggers are typically used to maintain data integrity and to enforce business rules.
Constraints and Views
- CREATE ASSERTION in SQL deals with integrity constraints, which are used to enforce data integrity by limiting the data that can be inserted, updated, or deleted in a database.
- Views can be used to simplify complex queries and to provide an additional layer of abstraction, which can improve database security.
View Maintenance
- The responsibility of keeping a view up-to-date in SQL lies with the database management system, which must recompute the view whenever the underlying data changes.
View Strategies
- The lazy or on-demand strategy involves computing the view as and when needed, without storing it permanently.
- The materialized strategy involves physically creating a temporary view table when the view is first queried.
View Clauses
- The WITH CHECK OPTION clause in SQL views ensures that any update operation on the view will successfully update the underlying base table.
Updating Views
- Update is not permitted on aggregate views in SQL when the view is defined using an aggregate function, such as SUM or AVG.
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Description
Test your knowledge about specifying semantic constraints as assertions, using triggers for actions, creating virtual tables (views) in SQL, and modifying schema in SQL. This quiz covers topics related to semantic constraints, views, and schema modification in SQL.
