Removing Primary Key Constraint in SQL Example
Let’s look at an example of removing the primary key constraint from a table in SQL.
Step 1: Create a Table with a Primary Key Constraint
Create a table with a primary key constraint using the following SQL query:
CREATE DATABASE w3wiki; USE w3wiki; CREATE TABLE student_details( stu_id VARCHAR(8) NOT NULL PRIMARY KEY, stu_name VARCHAR(20), stu_branch VARCHAR(20) );
Step 2: Check the Constraints of the Table
Use the following SQL query to check the constraints of the table:
SELECT * FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ;
Output:
Here in output ‘PK’ means primary key. The constraint can be known from the object explorer as well.
Step 3: Remove the Primary Key Constraint
Now, we will use the DROP CONSTRAINT to remove the primary key from the database.
ALTER TABLE student_details DROP CONSTRAINT PK__student___E53CAB21F07312DD
Step 4: Verify the Removal of the Primary Key Constraint
SELECT * FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ;
Output:
SQL Query to Remove Primary Key
The primary key is the key that may contain one or more columns that uniquely identify each row in a table. We can add a primary key constraint during table creation. To remove a primary key from a table, use the ALTER TABLE statement with the DROP CONSTRAINT clause.
Here, we will see how to remove a primary key constraint from a table in SQL.
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