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Chapter 14 - Sorting

• System Concepts– Sort key

• Major Key (Primary)• Minor Key (Secondary)

– Sort sequence• Ascending - Low to high• Descending – High to low

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Figure 14.1 Sorting Vocabulary

NAME YEAR MAJOR

Smith 1 Liberal artsJones 4 EngineeringAdams 3 BusinessHowe 2 Liberal artsFrank 1 EngineeringZev 4 BusinessBenjamin 4 BusinessGrauer 3 Liberal artsCrawford 2 EngineeringDeutsch 4 BusinessMakoske 1 Business

(a) Unsorted Data

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Primary Key: Name (Ascending)

NAME YEAR MAJOR

Adams 3 BusinessBenjamin 4 Business Crawford 2 EngineeringDeutsch 4 BusinessFrank 1 Engineering Grauer 3 Liberal arts Howe 2 Liberal artsJones 4 EngineeringMakoske 1 BusinessSmith 1 Liberal artsZev 4 Business

Figure 14.1 (b) Sorted Data, One Key

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Primary key: Year (descending)Secondary key: Name (ascending)

NAME YEAR MAJOR

Benjamin 4 Business Deutsch 4 BusinessJones 4 EngineeringZev 4 Business Adams 3 BusinessGrauer 3 Liberal arts Crawford 2 EngineeringHowe 2 Liberal artsFrank 1 Engineering Makoske 1 BusinessSmith 1 Liberal arts

Figure 14.1 Sorted Data, Two Keys

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Figure 14.1 Sorted Data, Three Keys

Primary Key: major (Ascending)Secondary Key: year (Descending)Tertiary Key: name (Ascending)

NAME YEAR MAJOR

Benjamin 4 Business Deutsch 4 BusinessZev 4 Business Adams 3 BusinessMakoske 1 Business Jones 4 Engineering Crawford 2 Engineering Frank 1 Engineering Grauer 3 Liberal arts Howe 2 Liberal artsSmith 1 Liberal arts

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– Collating Sequence (order of sorting)• Alphabetic fields

– Green vs. Greenfield

• Alphanumeric fields – 111 vs. AAA• EBCDIC sequence – IBM Mainframe• ASCII sequence – Most other computers

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EBCDIC

(space). (period, decimal point)< (less than)( (left parenthesis)+ (plus symbol)$ (currency symbol)* (asterisk)) (right parenthesis); (semicolon)- (hyphen, minus symbol)/ (slash), (comma)> (greater than)‘ (apostrophe)= (equal sign)“ (quotation mark)

a through z (lower case)A through Z (upper case)0 through 9

ASCII

(space)“ (quotation mark) $ (currency symbol)‘ (apostrophe) ( (left parenthesis) ) (right parenthesis) * (asterisk)+ (plus symbol) , (comma) - (hyphen, minus symbol) . (period, decimal point)/ (slash)

0 through 9; (semicolon)< (less than)= (equal sign)> (greater than)

A through Z (upper case)a through z (lower case)

Figure 14.2 EBCDIC & ASCII Collating Sequences

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• COBOL Implementation– SORT command

• Syntax• INPUT PROCEDURE statement

– Selective sorting– Sorting on calculated fields

• USING statement• OUTPUT PROCEDURE statement

– Use of temporary work file

• GIVING statement– Retention of sorted data

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SORT file-name-1

ON {DESCENDING KEY { data-name-1} . . . } ASCENDING}

WITH DUPLICATES IN ORDER

COLLATING SEQUENCE IS alphabet-name

INPUT PROCEDURE IS procedure-name-1USING {file-name-2}

OUTPUT PROCEDURE IS procedure-name-2GIVING {fine-name-3}

SORT syntax

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• Uses 3 files to sort– Input file – contains unsorted records– Output file – contains sorted records– Sort file – temporary file used by COBOL to

sort the records

• First 2 must be defined in the FD section

• Sort file must be defined in a SD section

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Input File Sort Output File

Sort file

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Ex.) SD SALESPERSON-SORT-FILE01 SALESPERSON-SORT-RECORD

05 SP-REGION PIC 99.

05 SP-NUMBER PIC XXXX.

05 FILLER PIC X(52).

…

SORT SALESPERSON-SORT-FILE

ON ASCENDING KEY SP-REGION SP-NUMBER

USING SALESPERSON-INPUT-FILE

GIVING SALESPERSON-OUTPUT-FILE

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SORT SALESPERSON-SORT-FILE

ON DESCENDING KEY SP-REGION

ON ASCENDING KEY SP-NUMBER

USING SALESPERSON-INPUT-FILE

GIVING SALESPERSON-OUTPUT-FILE

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Assume that the records in a file named X-FILE are to be sorted descending sequence by X-FIELD. The records in X-FILE are 40 characters long. X-FIELD is located in positions 8-12 and is alphanumeric. The file sorted output is called Y-FILE

a. Code the SD entry and record description

b. Code the sort statement

c. Assume is should be sorted into ascending sequence by Y-FIELD and then into descending sequence by X-FIELD. Code the sort statements.

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The registrar has asked for a simple report listing students by year, and alphabetically within year. Thus all freshmen are to appear first, then sophomores..The incoming record has the follow layout:

01 STUDENT-RECORD.

05 ST-NAME PIC X(15).

05 ST-MAJOR PIC X(15).

05 ST-YEAR PIC XX.

05 ST-CREDITS PIC X(10).

ST-YEAR USES FR,SO,JR AND GR. Develop the procedure division code to accomplish the desired sort.

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• Merge statement