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This chapter is from the book

This chapter is from the book

Getting Data Out of Databases

Suppose we wanted to produce a table of employees and their salary ranges for some planning exercise. This table doesn't exist directly in the database, but it can be constructed by issuing a query to the database. We'd like to have a table that looked like the data in Table 18-2.

Table 18-2. Employee Salaries Sorted by Name

Name

Min

Max

Adams

$45,000.00

$60,000.00

Johnson

$30,000.00

$45,000.00

Smyth

$60,000.00

$75,000.00

Tully

$30,000.00

$45,000.00

Wolff

$45,000.00

$60,000.00


Maybe we want data sorted by increasing salary, as shown in Table 18-3. We find that the query we issue to obtain these tables has this form.

Table 18-3. Employee Salaries Sorted by Magnitude

Name

Min

Max

Tully

$30,000.00

$45,000.00

Johnson

$30,000.00

$45,000.00

Wolff

$45,000.00

$60,000.00

Adams

$45,000.00

$60,000.00

Smyth

$60,000.00

$75,000.00


 SELECT DISTINCTROW Employees.Name, SalaryRanges.Min, 
 SalaryRanges.Max FROM Employees INNER JOIN SalaryRanges ON 
 Employees.SalaryKey = SalaryRanges.SalaryKey 
 ORDER BY SalaryRanges.Min; 

This language is called Structured Query Language or SQL (often pronounced "sequel"), and it is the language of virtually all databases currently available. There have been several standards issued for SQL over the years, and most PC databases support much of these ANSI standards. The SQL-92 standard is considered the floor standard, and there have been several updates since. However, not all databases support the later SQL versions perfectly, and most offer various kinds of SQL extensions to exploit various features unique to their database.

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