Which of the following is not Constraint in SQL? (amazon)Options: Pick one correct answer from belowPrimary KeyNot NullCheckUnion

Step 1: Break Down the Problem

We need to identify which option is not considered a constraint in SQL. The options provided are:

1. Primary Key
2. Not Null
3. Check
4. Union

Step 2: Relevant Concepts

• Primary Key: A constraint that uniquely identifies each record in a table.
• Not Null: A constraint that ensures a column cannot have a NULL value.
• Check: A constraint that ensures all values in a column satisfy a specific condition.
• Union: This is a SQL operation that combines the results of two or more SELECT statements, but it does not impose restrictions on the data.

Step 3: Analysis and Detail

• Primary Key is indeed a constraint, as it enforces uniqueness.
• Not Null is also a constraint, as it prevents NULL values from being inserted into columns.
• Check is a constraint that is used for validating data.
• Union is not a constraint but a set operation in SQL.

Step 4: Verify and Summarize

After analyzing the definitions and roles of each option, it is clear that all of the first three options (Primary Key, Not Null, and Check) are constraints in SQL, while Union is not.

Final Answer

The option that is not a constraint in SQL is Union.