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what is the difference between adding keys & constraints
into a phisical file
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Answer / jherie
A key field defines the order in which the records of a PF
member will be sorted (ascending or descending).
On the other hand, constraints, such as UNIQUE, defines
which key field values or records are valid/allowable to be
written into a file. UNIQUE prevents a record with
duplicate key field values to be written into a PF.
| Is This Answer Correct ? | 25 Yes | 0 No |
Answer / sweety joy
during the time of compilation of a file , constrains are
being removed, from the file .but at the time of
compliation keys are not removed in case from pf.
constraints has no affects on members of a pf but keys has
affect on members of pf
| Is This Answer Correct ? | 2 Yes | 2 No |
Answer / kkcode400
ADDING KEY FIELDS TO FILE IT DOES NOT CHECK THE EXISTING
DATA.
BUT CONSTRAINS CHECK THE EXISTING DATA BEFORE ADDING IT.
IF ANY DUPLICATE KEY VALUES ARE THERE OPERATION FAILURE.
| Is This Answer Correct ? | 1 Yes | 1 No |
Answer / kolla ravi
Primary Key - Unique Key - Key are all possible with DDS.
Either a primary or a Unique key as required can be setup
with UNIQUE keyword at file level in DDS.These keys Do not
allow any two records with same keys.
When UNIQUE is not used then FIFO or LIFO may be used. When
nothing is specified it is understood to be FIFO.
All these need Key fields to be specified.
And in addition to this whether primary/unique or just a
key, a key field dictates the order of retrieval of records
when programs read the files.
All these what we spoke above is done through DDS. That
is : all these stay right within the object.
On the other hand it is possible to setup Constraints
externally. These being Primary/Unique/Referetinal/Check.
Once these are defined they can be controlled Externally by
enabling, Disabling or removing them on the files for which
they are defined.In this context it is worth while
understanding various states of constraints and Upd/delete
rules in this context.
| Is This Answer Correct ? | 0 Yes | 1 No |
Answer / praseetha sandeep
when we add keys in a pf it has effect only in that
particular field of pf but when we add constrains to a pf it
has an effect to entire pf
| Is This Answer Correct ? | 3 Yes | 5 No |
Answer / suju
constraint wl effect the particular field,key wl effect the
whole pf.
| Is This Answer Correct ? | 1 Yes | 7 No |
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