MERGE statement

ASCENDING/DESCENDING KEY phrase

This phrase specifies that records are to be processed in an ascending or descending sequence (depending on the phrase specified), based on the specified merge keys.

data-name-1

Specifies a KEY data item on which the merge will be based. Each such data-name must identify a data item in a record associated with file-name-1. The data-names following the word KEY are listed from left to right in the MERGE statement in order of decreasing significance without regard to how they are divided into KEY phrases. The leftmost data-name is the major key, the next data-name is the next most significant key, and so forth.

The following rules apply:

• A specific key data item must be physically located in the same position and have the same data format in each input file. However, it need not have the same data-name.
• If file-name-1 has more than one record description, the KEY data items need be described in only one of the record descriptions.
• If file-name-1 contains variable-length records, all of the KEY data-items must be contained within the first n character positions of the record, where n equals the minimum records size specified for file-name-1.
• KEY data items must not contain an OCCURS clause or be subordinate to an item that contains an OCCURS clause.
• KEY data items cannot be:
  • Variably located
  • Group items that contain variable-occurrence data items
  • Category numeric described with usage NATIONAL (national decimal type)
  • Category external floating-point described with usage NATIONAL (national floating-point)
  • Category DBCS
• KEY data items can be qualified.
• KEY data items can be any of the following data categories:
  • Alphabetic, alphanumeric, alphanumeric-edited
  • Numeric (except numeric with usage NATIONAL)
  • Numeric-edited (with usage DISPLAY or NATIONAL)
  • Internal floating-point or display floating-point
  • National or national-edited

The direction of the merge operation depends on the specification of the ASCENDING or DESCENDING keywords as follows:

• When ASCENDING is specified, the sequence is from the lowest key value to the highest key value.
• When DESCENDING is specified, the sequence is from the highest key value to the lowest key value.

If the KEY data item is described with usage NATIONAL, the sequence of the KEY values is based on the binary values of the national characters.

When the COLLATING SEQUENCE phrase is not specified, the key comparisons are performed according to the rules for comparison of operands in a relation condition. For details, see General relation conditions.

When the COLLATING SEQUENCE phrase is specified, the indicated collating sequence is used for key data items of alphabetic, alphanumeric, alphanumeric-edited, external floating-point, and numeric-edited categories. For all other key data items, the comparisons are performed according to the rules for comparison of operands in a relation condition.

COLLATING SEQUENCE phrase

This phrase specifies the collating sequence to be used in alphanumeric comparisons for the KEY data items in this merge operation.

The COLLATING SEQUENCE phrase has no effect for keys that are not alphabetic or alphanumeric.

alphabet-name-1

Must be specified in the ALPHABET clause of the SPECIAL-NAMES paragraph. Any one of the alphabet-name clause phrases can be specified, with the following results:

STANDARD-1

The ASCII collating sequence is used for all alphanumeric comparisons. (The ASCII collating sequence is shown in US English ASCII code page.)

STANDARD-2

The 7-bit code defined in the International Reference Version of ISO/IEC 646, 7-bit coded character set for information interchange is used for all alphanumeric comparisons.

NATIVE

The EBCDIC collating sequence is used for all alphanumeric comparisons. (The EBCDIC collating sequence is shown in EBCDIC collating sequence.)

EBCDIC

The EBCDIC collating sequence is used for all alphanumeric comparisons. (The EBCDIC collating sequence is shown in EBCDIC collating sequence.)

literal

The collating sequence established by the specification of literals in the ALPHABET-NAME clause is used for all alphanumeric comparisons.

When the COLLATING SEQUENCE phrase is omitted, the PROGRAM COLLATING SEQUENCE clause (if specified) in the OBJECT-COMPUTER paragraph identifies the collating sequence to be used. When both the COLLATING SEQUENCE phrase of the MERGE statement and the PROGRAM COLLATING SEQUENCE clause of the OBJECT-COMPUTER paragraph are omitted, the EBCDIC collating sequence is used.

USING phrase

file-name-2 , file-name-3 , ...

Specifies the input files.

During the MERGE operation, all the records on file-name-2, file-name-3, ... (that is, the input files) are transferred to file-name-1. At the time the MERGE statement is executed, these files must not be open. The input files are automatically opened, read, and closed. If DECLARATIVE procedures are specified for these files for input operations, the declaratives will be driven for errors if errors occur.

All input files must specify sequential or dynamic access mode and be described in FD entries in the DATA DIVISION.

If file-name-1 contains variable-length records, the size of the records contained in the input files (file-name-2, file-name-3, ...) must be neither less than the smallest record nor greater than the largest record described for file-name-1. If file-name-1 contains fixed-length records, the size of the records contained in the input files must not be greater than the largest record described for file-name-1. For more information, see Sorting and merging files in the Enterprise COBOL Programming Guide.

GIVING phrase

file-name-4 , ...

Specifies the output files.

When the GIVING phrase is specified, all the merged records in file-name-1 are automatically transferred to the output files (file-name-4, ...).

All output files must specify sequential or dynamic access mode and be described in FD entries in the DATA DIVISION.

If the output files (file-name-4, ...) contain variable-length records, the size of the records contained in file-name-1 must be neither less than the smallest record nor greater than the largest record described for the output files. If the output files contain fixed-length records, the size of the records contained in file-name-1 must not be greater than the largest record described for the output files. For more information, see Sorting and merging files in the Enterprise COBOL Programming Guide.

At the time the MERGE statement is executed, the output files (file-name-4, ...) must not be open. The output files are automatically opened, read, and closed. If DECLARATIVE procedures are specified for these files for output operations, the declaratives will be driven for errors if errors occur.

OUTPUT PROCEDURE phrase

This phrase specifies the name of a procedure that is to select or modify output records from the merge operation.

procedure-name-1

Specifies the first (or only) section or paragraph in the OUTPUT PROCEDURE.

procedure-name-2

Identifies the last section or paragraph of the OUTPUT PROCEDURE.

The OUTPUT PROCEDURE can consist of any procedure needed to select, modify, or copy the records that are made available one at time by the RETURN statement in merged order from the file referenced by file-name-1. The range includes all statements that are executed as the result of a transfer of control by CALL, EXIT, GO TO, PERFORM, and XML PARSE statements in the range of the output procedure. The range also includes all statements in declarative procedures that are executed as a result of the execution of statements in the range of the output procedure. The range of the output procedure must not cause the execution of any MERGE, RELEASE, or format 1 SORT statement.

If an output procedure is specified, control passes to it after the file referenced by file-name-1 has been sequenced by the MERGE statement. The compiler inserts a return mechanism at the end of the last statement in the output procedure and when control passes the last statement in the output procedure, the return mechanism provides the termination of the merge and then passes control to the next executable statement after the MERGE statement. Before entering the output procedure, the merge procedure reaches a point at which it can select the next record in merged order when requested. The RETURN statements in the output procedure are the requests for the next record.

The OUTPUT PROCEDURE phrase is similar to a basic PERFORM statement. For example, if you name a procedure in an OUTPUT PROCEDURE, that procedure is executed during the merging operation just as if it were named in a PERFORM statement. As with the PERFORM statement, execution of the procedure is terminated after the last statement completes execution. The last statement in an OUTPUT PROCEDURE can be the EXIT statement (see EXIT statement).