Case 1: Matching records in primary and secondary files

 

This example join logical file contains a single record for each record in the primary file because each record in the primary file has a match in the secondary file.

Assume that a join logical file is specified as in Example 1: Basic concepts of joining two physical files, and four records are contained in both PF1 and PF2, as shown in the following two tables.

Table 1. Physical file 1 (PF1)

Employee number	Name
235	Anne
440	Doug
500	Mark
729	Sue

Table 2. Physical file 2 (PF2)

Employee number	Salary
235	1700.00
440	950.50
500	2100.00
729	1400.90

The program does four read operations and gets the following records.

Table 3. Join logical file (JLF)

Employee number	Name	Salary
235	Anne	1700.00
440	Doug	950.50
500	Mark	2100.00
729	Sue	1400.90

 

Parent topic:

Example 1: Basic concepts of joining two physical files