Question

What is an input mask used for? What is the purpose of a primary key? Why is redundancy of data undesirable? What is a wildcard character? How would you use it to find a record?

Answer 1

Answer:

Input mask is basically a string of characters which indicates the format of all the valid input values. It is used in query fields, table fields and also controls on form and reports. Input mask is also stored as an object property. Input mask is very important when the format of taken input values are consistent.

The purpose of primary key is to ensure that the data in a specific coloumn is Unique. We can only set constraints with the use of primary keys, by setting a foreign key to the another column which creates a relationship with the column that has the primary key set.

Redundancy basically means that, having multiple number of copies of the same data in a the database. This problem arises only when a database is not normalized. The redundancy of data is undesirable because it can occur due to many uncertainities such as overcomplicated storing of data or insufficient coding and then it represents an issue in terms of efficiency and cost.

A Wildcard character is a special character which represents more than one characters. The most common wildcard character is asterisk (*) sign. which generally represents zero or more characters present in a string of characters. A wildcard character can be used for compairison criteria when we are searching. It is also used in SQL as a part of WHERE clause to find the all records.

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