Chapter 9: Problem 1

How does SQL allow implementation of general integrity constraints?

Short Answer

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SQL allows implementation of general integrity constraints through the use of domain, entity, and referential integrity along with Check Constraints. Domain integrity is integrated by defining the data type for the columns, and entity integrity by defining unique primary key values for each row. Referential integrity is done using foreign keys that relate to primary keys in other tables, and check constraints are used to set specific conditions for the data that needs to be fulfilled.

Step by step solution

Understand SQL Integrity Constraints

Integrity constraints are rules that help to ensure the quality of the information stored in the database. The three types of integrity constraints predominantly used in SQL are Domain, Entity and Referential integrity constraints.

Implementation of Domain Integrity

Domain Integrity involves checks on the type of data entered. This is usually done by defining the data type and possible values for the columns while creating the tables. Numeric columns can have checks on the range of values allowed.

Implementation of Entity Integrity

Entity Integrity involves ensuring the uniqueness of rows in a table. This can be done by defining one or more columns as Primary key, which forces every row to have a unique value for the designated columns. This can be implemented in SQL using CREATE TABLE command followed by column name and PRIMARY KEY keyword.

Implementation of Referential Integrity

Referential Integrity involves ensuring the relationship between columns in tables. Usually, it is implemented using foreign key constraints on the columns that relate to primary key columns in other tables. Foreign key constraint in SQL is usually added using FOREIGN KEY keyword followed by column name, REFERENCES keyword and respective parent table name.

Assignment of Check Constraints

Check constraints can be used to assign more specific conditions that data in the tables must fulfil. Typically, this is done using the CHECK keyword while defining the table. The CHECK constraint makes sure that all values in a column or set of columns fulfill a specific condition set by the database designer.

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How does SQL allow implementation of general integrity constraints?

Short Answer

Step by step solution

Understand SQL Integrity Constraints

Implementation of Domain Integrity

Implementation of Entity Integrity

Implementation of Referential Integrity

Assignment of Check Constraints

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