Example 9: Using defaults for missing records from secondary files

 

This example shows how to use the default value for a missing join field in a secondary file to join to the other secondary file.

If the DFT keyword is specified in the secondary file, the value specified for the DFT keyword is used in the logical file.

The data description specifications (DDS) for the files are shown as follows:

JLF
|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
     A                                      JDFTVAL      A          R JRCD                      JFILE(PF1 PF2 PF3)
     A          J                           JOIN(PF1 PF2)
     A                                      JFLD(NAME NAME)
     A          J                           JOIN(PF2 PF3)
     A                                      JFLD(TELEPHONE TELEPHONE)
     A            NAME                      JREF(PF1)
     A            ADDR      A            TELEPHONE                 JREF(PF2)
     A            LOC      A  

PF1
|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
     A          R RCD1
     A            NAME          20
     A            ADDR          40
     A            COUNTRY       40
     A  

PF2
|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
     A          R RCD2
     A            NAME          20
     A            TELEPHONE      8          DFT('999-9999')
     A  

PF3
|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
     A          R RCD3
     A            TELEPHONE      8
     A            LOC           30          DFT('No location assigned')
     A

Assume that PF1, PF2, and PF3 have the following records.

Table 1. Physical file 1 (PF1)

Name	Address	Country
Anne	120 1st St.	USA
Doug	40 Pillsbury	Canada
Mark	2 Lakeside Dr.	Canada
Sue	120 Broadway	USA

Table 2. Physical file 2 (PF2)

Name	Telephone
Anne	555–1234
Doug	555–2222
Sue	555–1144

Table 3. Physical file 3 (PF3)

Telephone	Location
555–1234	Room 312
555–2222	Main lobby
999–9999	No telephone number

With JDFTVAL specified in the join logical file, the program reads the following logical file records.

Table 4. Join logical file (JLF)

Name	Address	Telephone	Location
Anne	120 1st St.	555–1234	Room 312
Doug	40 Pillsbury	555–2222	Main lobby
Mark	2 Lakeside Dr.	999–9999	No telephone number
Sue	120 Broadway	555–1144	No location assigned

In this example, complete data is found for Anne and Doug. However, part of the data is missing for Mark and Sue.

• PF2 is missing a record for Mark because he has no telephone number. The default value for the Telephone field in PF2 is defined as 999-9999 using the DFT keyword. In this example, therefore, 999-9999 is the telephone number returned when no telephone number is assigned. The JDFTVAL keyword specified in the join logical file causes the default value for the Telephone field (which is 999-9999) in PF2 to be used to match with a record in PF3. (In PF3, a record is included to show a description for telephone number 999-9999.) Without the JDFTVAL keyword, no record would be returned for Mark.

• Sue's telephone number is not yet assigned a location; therefore, a record for 555-1144 is missing in PF3. Without JDFTVAL specified, no record would be returned for Sue. With JDFTVAL specified, the system supplies the default value specified on the DFT keyword in PF3 the Loc field (which is No location assigned).

 

Parent topic:

Setting up a join logical file