Sybase 12.4.2 manual Data integrity overview, How data can become invalid, 273

C H A P T E R 7 Ensuring Data Integrity

About this chapter	This chapter describes facilities for ensuring that the data in your database
	is valid and reliable. These facilities include constraints on tables and
	columns, and choosing appropriate data types.
	The SQL statements in this chapter use the CREATE TABLE statement
	and ALTER TABLE statement, basic forms of which were introduced in
	Chapter 3, “Working with Database Objects”

Data integrity overview

For data to have integrity means that the data is valid—that is, correct and accurate—and that the relational structure of the database is intact. The relational structure of the database is described through referential integrity constraints, business rules that maintain the consistency of data between tables.

Adaptive Server IQ supports stored procedures and JDBC, which allow you detailed control over how data gets entered into the database. Procedures are discussed in Chapter 6, “Using Procedures and Batches” See the Adaptive Server Anywhere User’s Guide for information on JDBC.

How data can become invalid

Here are a few examples of how the data in a database may become invalid if proper checks are not made. Each of these examples can be prevented by facilities described in this chapter.

Incorrectly formatted	•	An operator enters text where numeric data is required.
information	•	An operator enters numeric data that is too wide for the column.
Duplicated data	•	A new department has been created, with dept_id 200, and needs to
		be added to the department table of the organization's database—but
		two people enter this information into the table.

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