DATABASE FUNDAMENTALS
WHAT IS DATABASE MANAGEMENT
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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One way to restrict input in a table field
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The field which we will use to search with
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A field that contains unique data in each record
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The first field in a table
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Detailed explanation-1: -A primary key is the column or columns that contain values that uniquely identify each row in a table. A database table must have a primary key for Optim to insert, update, restore, or delete data from a database table. Optim uses primary keys that are defined to the database.
Detailed explanation-2: -Primary Key-a field containing a value that uniquely identifies each record in a table. The primary key is unique and prevents entering duplicate records or a null value in that field. Foreign Key-a key in a related table that refers to the primary key in another table.
Detailed explanation-3: -A primary key consists of one or more fields that uniquely identify each record that you store in the table. Often, there is a unique identification number, such as an ID number, a serial number, or a code, that serves as a primary key.
Detailed explanation-4: -The primary key is accepted as a unique or sole identifier for every record in the table. In the case of a primary key, we cannot save NULL values. In the case of a unique key, we can save a null value, however, only one NULL value is supported.
Detailed explanation-5: -b) Unique can have single NULL value but Primary can’t have even single. Explanation: Primary key doesn’t allow Null values and Unique key allows Null value, but only one Null value.