Which of the following is NOT a type of SQL constraint? UNIQUEPRIMARY KEYALTERNATE KEYFOREIGN KEY

To determine which option is not a type of SQL constraint, let's analyze each of the provided options:

1. UNIQUE: This is a type of constraint that ensures all values in a column are different from each other. It can be applied to a single column or a group of columns in a table.

2. PRIMARY KEY: This is a type of constraint that uniquely identifies each row in a database table. A table can have only one primary key, which can consist of one or more columns.

3. ALTERNATE KEY: This is not a standard SQL constraint defined in SQL specifications. Instead, it is often a term used to describe any candidate key that is not chosen as the primary key but is still unique.

4. FOREIGN KEY: This constraint is used to establish a relationship between two tables, ensuring that values in one table correspond to values in another.

Final Answer

The option that is NOT a type of SQL constraint is ALTERNATE KEY.