How to Add Primary Key Constraint on Oracle?

To add a primary key constraint on Oracle, you can use the ALTER TABLE statement followed by the ADD CONSTRAINT keyword. Specify the name of the primary key constraint and the column(s) that make up the primary key. For example, to add a primary key constraint named PK_Employee_ID on the Employee_ID column in the Employees table, you would use the following SQL statement:

ALTER TABLE Employees ADD CONSTRAINT PK_Employee_ID PRIMARY KEY (Employee_ID);

Make sure that the column or columns specified for the primary key do not contain any duplicate or null values. Additionally, the primary key constraint will automatically create an index on the columns to enforce uniqueness and improve query performance.

What is the purpose of primary key constraint in database design?

The purpose of a primary key constraint in database design is to uniquely identify each record in a table. It ensures that each record in the table has a unique identifier, which helps to maintain data integrity and prevent duplicate records. The primary key constraint also allows for efficient indexing and querying of the data in the table. It is an important aspect of relational database design as it helps to establish relationships between tables and enforce data integrity rules.

What is the role of primary key constraint in data integrity in Oracle?

In Oracle, a primary key constraint plays a crucial role in ensuring data integrity within a database.

The primary key constraint uniquely identifies each record in a table and ensures that each record has a unique identifier. It enforces the uniqueness of values in a specific column or combination of columns, thereby preventing duplicate entries in the table.

By enforcing the primary key constraint, Oracle ensures data consistency and prevents data corruption or loss. It also helps maintain referential integrity by allowing other tables to establish relationships with the primary key column(s) of a table.

In summary, the primary key constraint in Oracle helps maintain the integrity of data by ensuring uniqueness and establishing relationships between tables.

How to manage primary key constraint conflicts in Oracle?

There are several ways to manage primary key constraint conflicts in Oracle:

1. Use the INSERT IGNORE statement: You can use the INSERT IGNORE statement to insert a new record into a table without causing the primary key constraint violation. This will ignore the insertion of the record if it violates the primary key constraint.
2. Use the MERGE statement: The MERGE statement allows you to update existing records or insert new records into a table without causing primary key constraint violations. It merges the data from the source table into the target table and handles conflicts accordingly.
3. Use the ON DUPLICATE KEY UPDATE clause: If you are using the INSERT statement to insert data into a table, you can use the ON DUPLICATE KEY UPDATE clause to update the existing record if a primary key constraint violation occurs.
4. Use PL/SQL exception handling: You can write PL/SQL code to handle primary key constraint violations by using exception handling. This will allow you to catch the error and take appropriate action, such as logging the error or rolling back the transaction.
5. Use a sequence: Instead of relying on manually generated primary key values, you can use a sequence to automatically generate unique primary key values for each record. This will help prevent primary key constraint conflicts from occurring.

Overall, these are some ways to manage primary key constraint conflicts in Oracle. Each approach has its advantages and disadvantages, so it's important to choose the method that best suits your specific requirements.