ITPEC IP April 2018 Question 28
When the order records shown below are entered in the system where each order number must be uniquely assigned, which of the following is the appropriate method for searching the order master file containing all of the past order records, and for checking the uniqueness of the order number?
Order record
Explanation
Duplicate check — searching the existing records to confirm a key value is not already in use.
The order number must be unique. Before a new order is accepted, the system looks up its order number in the order master file of all past orders; if the number is already there, the input is rejected as a duplicate.
Answer (a)
Why not others:
- •(b) Format check — tests whether the data has the right form, such as digits only or a valid Year/Month/Day date; it does not look at other records
- •(c) Limit check — tests whether a value lies within an allowed range, such as a quantity from 1 to 999
- •(d) Logical check — tests whether a value is consistent with a rule or with other items, such as an order date not later than the entry date
Key rule: Only a duplicate check compares the input with data already stored; format, limit and logical checks look at the input itself.
Human Interface · AI-written, may contain errors
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