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Process Help DIFFRN - relational difference operation on two sorted files |
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Process Name |
Menu Path |
Link to Command Table |
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DIFFRN |
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Introduction
Performs a relational difference operation.
How to use
Records from the first input file are copied to the output file only if there is no match between the keyfields of the first and second input files. The effect is to delete records from the first input file if they are matched with the entries in the second input file, using the keyfields as the match criteria. Thus differencing is essentially a record deletion mechanism.
At least one keyfield must be specified and must appear in both input files as an explicit field. The keyfield may be up to 5 words long, and may be composed of up to 5 fields. If a field is specified which does not exist in both input files, it is ignored, providing at least one field matches.
Both input files must be sorted in the order of the keyfields before they can be differenced. If this is not the case, the process will exit with an error message.
A typical use of the DIFFRN process is to delete drillholes from a file by supplying a set of borehole identifiers as the second input file.
Files, Fields and Parameters
Input Files
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Name |
Description |
I/O Status |
Required |
Type |
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IN1 |
File to have records deleted (sorted on required keyfields). |
Input |
Yes |
Undefined |
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IN2 |
File containing keyfield values for deletion (sorted on required keyfields). |
Input |
Yes |
Undefined |
Output Files
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Name |
I/O Status |
Required |
Type |
Description |
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OUT |
Output |
Yes |
Undefined |
Output file. |
Fields
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Name |
Description |
Source |
Required |
Type |
Default |
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KEY1 |
Keyfield 1 for file matching. |
IN1, IN2 |
Yes |
Any |
Undefined |
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KEY2 |
Keyfield 2. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY3 |
Keyfield 3. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY4 |
Keyfield 4. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY5 |
Keyfield 5. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY6 |
Keyfield 6. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY7 |
Keyfield 7. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY8 |
Keyfield 8. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY9 |
Keyfield 9. |
IN1, IN2 |
No |
Any |
Undefined |
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KEY10 |
Keyfield 10. |
IN1, IN2 |
No |
Any |
Undefined |
Parameters
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Name |
Description |
Required |
Default |
Range |
Values |
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KEYTOL |
KEYTOL is the tolerance value used to test whether numeric key values are equal. It must be greater than or equal to zero. It replaces the previous heuristic comparison method. If KEYTOL is set to a negative value then zero is used. In a macro KEYTOL can be set to absent using -. "@KEYTOL=-" This will revert to legacy behaviour and use a heuristic comparison in relational commands and zero in sort. |
No |
0.00001 |
0,+ |
Undefined |
Notes
No additional notes.
Example
!DIFFRN &IN1(FILE), &IN2(BHIDS), &OUT(FILE1), *KEY1(BHID)
Error and Warning Messages
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Message |
Description |
Solution |
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>>> ERR 47 <<< ( 0) IN FNDKEY |
Warning; none of the specified key fields exist in the input files. An output file is produced consisting only of a Data Definition containing the fields of both input files.
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>>> KEYFIELD nnnnnnnn MISSING FROM FILE ffffffff |
A warning message that is produced if @PRINT >=1. The keyfield is ignored and processing continues. |
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>>> ERR 121 <<< ( fileno) IN DIFFRN |
One (or both) of the input files is empty. Fatal; the process is exited. |
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>>> INPUT FILE NOT SORTED ON KEYFIELD |
One (or both) of the input files is not sorted on the designated keyfields. Fatal; the process is exited. |
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