Concatenated fields

Using the CONCAT keyword, you can combine two or more fields from a physical file record format to make one field in a logical file record format.

For example, a physical file record format contains the fields Month, Day, and Year. For a logical file, you concatenate these fields into one field, Date.

The field length for the resulting concatenated field is the sum of the lengths of the included fields (unless the fields in the physical file are binary or packed decimal, in which case they are changed to zoned decimal). The field length of the resulting field is automatically calculated by the system. A concatenated field can have:

Column headings
Validity checking
Text description
Edit code or edit word (numeric concatenated fields only)

Note: This editing and validity checking information is not used by the database management system but is retrieved when field descriptions from the database file are referred to in a display or printer file.

When fields are concatenated, the data types can change (the resulting data type is automatically determined by the system). The following rules and restrictions apply:

The operating system assigns the data type based on the data types of the fields that are being concatenated.
The maximum length of a concatenated field varies depending on the data type of the concatenated field and the length of the fields being concatenated. If the concatenated field is zoned decimal (S), its total length cannot exceed 31 bytes; if it is character (A), its total length cannot exceed 32 766 bytes.
In join logical files, the fields to be concatenated must be from the same physical file. The first field specified on the CONCAT keyword identifies which physical file is to be used. The first field must, therefore, be unique among the physical files on which the logical file is based, or you must also specify the JREF keyword to specify which physical file to use.
The use of a concatenated field must be I (input only) if the concatenated field is variable length. Otherwise, the use can be B (both input and output).
REFSHIFT cannot be specified on a concatenated field that has been assigned a data type of O or J.
If any of the fields contain the null value, the result of concatenation is the null value.

Note: For information about concatenating DBCS fields, see Double-byte character set considerations.

When only numeric fields are concatenated, the sign of the last field in the group is used as the sign of the concatenated field.

Notes:

Numeric fields with decimal precision other than zero cannot be included in a concatenated field.
Date, time, timestamp, and floating-point fields cannot be included in a concatenated field.

The following example shows the field description in data description specifications (DDS) for concatenation. (The CONCAT keyword is used to specify the fields to concatenate.)

|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
     A
00101A            MONTH
00102A            DAY
00103A            YEAR
00104A            DATE                      CONCAT(MONTH DAY YEAR)
     A

In this example, the logical file record format includes the separate fields of Month, Day, and Year, as well as the concatenated Date field. Any of the following formats can be used:

A format with the separate fields of Month, Day, and Year
A format with only the concatenated Date field
A format with the separate fields Month, Day, Year and the concatenated Date field

When both separate and concatenated fields exist in the format, any updates to the fields are processed in the sequence in which the DDS is specified. In the previous example, if the Date field contained 103188 and the Month field is changed to 12, when the record is updated, the month in the Date field would be used. The updated record would contain 103188. If the Date field were specified first, the updated record would contain 123188.

Concatenated fields can also be used as key fields and select/omit fields.