Assigning Match Field Values (M1-M9)
Assigning Match Field Values (M1-M9)
When assigning match field values (M1 through M9) to fields on the input specifications in positions 65 and 66, consider the following:
- Sequence checking is done for all record types with match field specifications. All match fields must be in the same order, either all ascending or all descending. The contents of the fields to which M1 through M9 are assigned are checked for correct sequence. An error in sequence causes the RPG IV exception/error handling routine to receive control. When the program continues processing, the next record from the same file is read.
- Not all files used in the program must have match fields. Not all record types within one file must have match fields either. However, at least one record type from two files must have match fields if files are ever to be matched.
- The same match field values must be specified for all record types that are used in matching. See Figure 1.
- Date, time, and timestamp match fields with the same match field values (M1 through M9) must be the same type (for example, all date) but can be different formats.
- All character, graphic, or numeric match fields with the same match field values (M1 through M9) should be the same length and type. If the match field contains packed data, the zoned decimal length (two times packed length - 1) is used as the length of the match field. It is valid to match a packed field in one record against a zoned decimal field in another if the digit lengths are identical. The length must always be odd because the length of a packed field is always odd.
- Record positions of different match fields can overlap, but the total length of all fields must not exceed 256 characters.
- If more than one match field is specified for a record type, all the fields are combined and treated as one continuous field (see Figure 1). The fields are combined according to descending sequence (M9 to M1) of matching field values.
- Match fields values cannot be repeated in a record.
- All match fields given the same matching field value (M1 through M9) are considered numeric if any one of the match fields is described as numeric.
- When numeric fields having decimal positions are matched, they are treated as if they had no decimal position. For instance 3.46 is considered equal to 346.
- Only the digit portions of numeric match fields are compared. Even though a field is negative, it is considered to be positive because the sign of the numeric field is ignored. Therefore, a -5 matches a +5.
- Date and time fields are converted to *ISO format for comparisons
- Graphic data is compared hexadecimally
- Whenever more than one matching field value is used, all match fields must match before the MR indicator is set on. For example, if match field values M1, M2, and M3 are specified, all three fields from a primary record must match all three match fields from a secondary record. A match on only the fields specified by M1 and M2 fields will not set the MR indicator on (see Figure 1).
- UCS-2 fields cannot be used for matching fields.
- Matching fields cannot be used for lookahead fields, and arrays.
- Field names are ignored in matching record operations. Therefore, fields from different record types that are assigned the same match level can have the same name.
- If an alternate collating sequence or a file translation is defined for the program, character fields are matched according to the alternate sequence specified.
- Null-capable fields, character fields defined with ALTSEQ(*NONE), and binary, float, integer and unsigned fields (B, F, I, or U in position 36 of the input specifications) cannot be assigned a match field value.
- Match fields that have no field record relation indicator must be described before those that do. When the field record relation indicator is used with match fields, the field record relation indicator should be the same as a record identifying indicator for this file, and the match fields must be grouped according to the field record relation indicator.
- When any match value (M1 through M9) is specified for a field without a field record relation indicator, all match values used must be specified once without a field record relation indicator. If all match fields are not common to all records, a dummy match field should be used. Field record relation indicators are invalid for externally described files. (see Figure 2).
- Match fields are independent of control level indicators (L1 through L9).
- If multi-file processing is specified and the LR indicator is set on, the program bypasses the multi-file processing routine.
Figure 1 is an example of how match fields are specified.
Figure 1. Match Fields in Which All Values Match
*...1....+....2....+....3....+....4....+....5....+....6....+....7...
FFilename++IPEASFRlen+LKlen+AIDevice+.Keywords++++++++++++++++++++++++++++
* The files in this example are externally described (E in position
* 22) and are to be processed by keys (K in position 34).
FMASTER IP E K DISK
FWEEKLY IS E K DISK
*...1....+....2....+....3....+....4....+....5....+....6....+....7...
IRcdname+++....Ri........................................................
I..............Ext-field+..................Field+++++++++L1M1..PlMnZr....
* MASTER FILE
IEMPMAS 01
I EMPLNO M1
I DIVSON M3
I DEPT M2
IDEPTMS 02
I EMPLNO M1
I DEPT M2
I DIVSON M3
* WEEKLY FILE
IWEEKRC 03
I EMPLNO M1
I DIVSON M3
I DEPT M2Three files are used in matching records. All the files have three match fields specified, and all use the same values (M1, M2, M3) to indicate which fields must match. The MR indicator is set on only if all three match fields in either of the files EMPMAS and DEPTMS are the same as all three fields from the WEEKRC file.
The three match fields in each file are combined and treated as one match field organized in the following descending sequence:
DIVSON : M3
DEPT : M2
EMPLNO : M1
The order in which the match fields are specified in the input specifications does not affect the organization of the match fields.
Figure 2. Match Fields with a Dummy M2 Field
*...1....+....2....+....3....+....4....+....5....+....6....+....7...
IFilename++SqNORiPos1+NCCPos2+NCCPos3+NCC................................
I........................Fmt+SPFrom+To+++DcField+++++++++L1M1FrPlMnZr....
IDISK AB 01 1 C1
I OR 02 1 C2
I OR 03 1 C3
I 1 10 0EMPNO M1
I 11 15 0DUMMY M2
I 11 15 0DEPT M202
I 16 20 0DEPT M203Three different record types are found in the input file. All three contain a match field in positions 1 through 10. Two of them have a second match field. Because M1 is found on all record types, it can be specified without a field record relation entry in positions 67 and 68. If one match value (M1 through M9) is specified without field record relation entries, all match values must be specified once without field record relation entries. Because the value M1 is specified without field record relationship, an M2 value must also be specified once without field record relationship. The M2 field is not on all record types; therefore a dummy M2 field must be specified next. The dummy field can be given any unique name, but its specified length must be equal to the length of the true M2 field. The M2 field is then related to the record types on which it is found by field record relation entries.
Figure 3. Match Field Specifications for Three Disk Files
*...1....+....2....+....3....+....4....+....5....+....6....+....7...
FFilename++IPEASFRlen+LKlen+AIDevice+.Keywords++++++++++++++++++++++++++++
FPRIMARY IPEA F 64 DISK
FFIRSTSEC IS A F 64 DISK
FSECSEC IS A F 64 DISK
*...1....+....2....+....3....+....4....+....5....+....6....+....7...
IFilename++SqNORiPos1+NCCPos2+NCCPos3+NCC................................
I........................Fmt+SPFrom+To+++DcField+++++++++L1M1FrPlMnZr....
IPRIMARY AA 01 1 CP 2NC
I 2 3 MATCH M1
*
I BB 02 1 CP 2 C
I 2 3 NOM
*
IFIRSTSEC AB 03 1 CS 2NC
I 2 3 MATCH M1
*
I BC 04 1 CS 2 C
I 2 3 NOM
*
ISECSEC AC 05 1 CT 2NC
I 2 3 MATCH M1
*
I BD 06 1 CT 2 C
I 2 3 NOM