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What does the check constraint do in SQL?
- a)It ensures that the values in a column are unique.
- b)It defines a column or a set of columns that uniquely identifies each row in a table.
- c)It establishes a relationship between two tables.
- d)It imposes a condition that must be satisfied by the values in a column.
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
What does the check constraint do in SQL?a)It ensures that the values ...
A check constraint imposes a condition that must be satisfied by the values in a column.
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What does the check constraint do in SQL?a)It ensures that the values ...
The check constraint in SQL is a feature that allows you to impose a condition or a set of conditions on the values in a column of a database table. It ensures that the data entered into the column satisfies the specified condition(s), and if not, it rejects the insertion or modification of the data.
Usage and Syntax:
The check constraint is defined at the column level and is specified within the CREATE TABLE statement. The syntax for creating a check constraint is as follows:
CREATE TABLE table_name (
column1 data_type CONSTRAINT constraint_name CHECK (condition),
column2 data_type,
...
);
Functionality and Purpose:
The primary purpose of a check constraint is to enforce data integrity by imposing restrictions on the values that can be inserted or updated in a column. It allows you to define rules that the data must adhere to, ensuring that only valid and meaningful data is stored in the database.
Examples:
Let's consider an example to understand the concept better. Suppose we have a table called "Employees" with a column named "Age". We want to ensure that the age of an employee must be between 18 and 60. We can use a check constraint to enforce this condition as follows:
CREATE TABLE Employees (
EmployeeID INT PRIMARY KEY,
Age INT CHECK (Age >= 18 AND Age <=>
Name VARCHAR(50),
...
);
Now, whenever a new employee is inserted or an existing employee's age is updated, the check constraint will verify if the age falls within the specified range. If the condition is not met, the operation will be rejected, and an error will be thrown.
Advantages:
- Data Integrity: Check constraints help maintain the integrity of the data by ensuring that only valid values are stored in the database.
- Simplified Validation: Instead of performing complex data validation checks in application code, the database itself handles the validation through check constraints.
- Improved Performance: By enforcing data restrictions at the database level, unnecessary data validation within application code can be avoided, leading to improved performance.
In conclusion, the check constraint in SQL imposes a condition that must be satisfied by the values in a column. It is a powerful tool for maintaining data integrity and ensuring the validity of the data stored in the database.
Usage and Syntax:
The check constraint is defined at the column level and is specified within the CREATE TABLE statement. The syntax for creating a check constraint is as follows:
CREATE TABLE table_name (
column1 data_type CONSTRAINT constraint_name CHECK (condition),
column2 data_type,
...
);
Functionality and Purpose:
The primary purpose of a check constraint is to enforce data integrity by imposing restrictions on the values that can be inserted or updated in a column. It allows you to define rules that the data must adhere to, ensuring that only valid and meaningful data is stored in the database.
Examples:
Let's consider an example to understand the concept better. Suppose we have a table called "Employees" with a column named "Age". We want to ensure that the age of an employee must be between 18 and 60. We can use a check constraint to enforce this condition as follows:
CREATE TABLE Employees (
EmployeeID INT PRIMARY KEY,
Age INT CHECK (Age >= 18 AND Age <=>
Name VARCHAR(50),
...
);
Now, whenever a new employee is inserted or an existing employee's age is updated, the check constraint will verify if the age falls within the specified range. If the condition is not met, the operation will be rejected, and an error will be thrown.
Advantages:
- Data Integrity: Check constraints help maintain the integrity of the data by ensuring that only valid values are stored in the database.
- Simplified Validation: Instead of performing complex data validation checks in application code, the database itself handles the validation through check constraints.
- Improved Performance: By enforcing data restrictions at the database level, unnecessary data validation within application code can be avoided, leading to improved performance.
In conclusion, the check constraint in SQL imposes a condition that must be satisfied by the values in a column. It is a powerful tool for maintaining data integrity and ensuring the validity of the data stored in the database.
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What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer?
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What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer?.
What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer? for Software Development 2025 is part of Software Development preparation. The Question and answers have been prepared according to the Software Development exam syllabus. Information about What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Software Development 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for What does the check constraint do in SQL?a)It ensures that the values in a column are unique.b)It defines a column or a set of columns that uniquely identifies each row in a table.c)It establishes a relationship between two tables.d)It imposes a condition that must be satisfied by the values in a column.Correct answer is option 'D'. Can you explain this answer?.
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