To add a unique constraint to a column in SQL, you use the `UNIQUE` keyword. This constraint ensures that all values in a column are distinct, meaning no duplicates are allowed. Here’s why the other options are not correct:

1. **CHECK**: This constraint is used to limit the values that can be placed in a column based on a specified condition but does not enforce uniqueness.

2. **PRIMARY KEY**: This constraint combines the unique constraint with the not-null constraint, meaning that it must contain unique values and cannot contain NULL. While a primary key does ensure uniqueness, it is specifically used for defining the primary identifier for a table.

3. **CONSTRAINT**: This is a generic term used for defining various types of constraints in SQL, including unique constraints, but it is not the specific keyword to apply a unique constraint on its own.

### Final Answer
The correct answer is **UNIQUE**.

Question

To add a unique constraint to a column in SQL, you use the `UNIQUE` keyword. This constraint ensures that all values in a column are distinct, meaning no duplicates are allowed. Here’s why the other options are not correct:

1. **CHECK**: This constraint is used to limit the values that can be placed in a column based on a specified condition but does not enforce uniqueness.
   
2. **PRIMARY KEY**: This constraint combines the unique constraint with the not-null constraint, meaning that it must contain unique values and cannot contain NULL. While a primary key does ensure uniqueness, it is specifically used for defining the primary identifier for a table.

3. **CONSTRAINT**: This is a generic term used for defining various types of constraints in SQL, including unique constraints, but it is not the specific keyword to apply a unique constraint on its own.

### Final Answer
The correct answer is **UNIQUE**.

Knowee AI · Accepted Answer

To add a unique constraint to a column in SQL, you use the `UNIQUE` keyword. This constraint ensures that all values in a column are distinct, meaning no duplicates are allowed. Here’s why the other options are not correct:

1. **CHECK**: This constraint is used to limit the values that can be placed in a column based on a specified condition but does not enforce uniqueness.
   
2. **PRIMARY KEY**: This constraint combines the unique constraint with the not-null constraint, meaning that it must contain unique values and cannot contain NULL. While a primary key does ensure uniqueness, it is specifically used for defining the primary identifier for a table.

3. **CONSTRAINT**: This is a generic term used for defining various types of constraints in SQL, including unique constraints, but it is not the specific keyword to apply a unique constraint on its own.

### Final Answer
The correct answer is **UNIQUE**.

ct the correct answerWhat SQL statement is used to add a unique constraint to a column?OptionsUNIQUECHECKPRIMARY KEYCONSTRAINT

Question

What SQL statement is used to add a unique constraint to a column?

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Final Answer

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