COMPUTER SCIENCE AND ENGINEERING
SQL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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NULL
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” “
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0
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N/A
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Detailed explanation-1: -A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL value. Note: A NULL value is different from a zero value or a field that contains spaces.
Detailed explanation-2: -A null value in a relational database is used when the value in a column is unknown or missing. A null is neither an empty string (for character or datetime data types) nor a zero value (for numeric data types).
Detailed explanation-3: -A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A primary key column cannot have NULL values.
Detailed explanation-4: -An empty string is a string instance of zero length. However, a NULL has no value at all.
Detailed explanation-5: -The answer to that is rather simple: a NULL means that there is no value, we’re looking at a blank/empty cell, and 0 means the value itself is 0.