Introduction:
In any database management system, CRUD operations play a crucial role in manipulating data. CRUD stands for Create, Read, Update, and Delete. These operations allow you to interact with the database and perform tasks such as inserting new data, retrieving existing data, updating data, and deleting data. In this article, we will focus on CRUD operations specifically in Oracle, one of the most popular database systems in the market.
SELECT Statement:
The SELECT statement is used to retrieve data from one or more tables in the database. It allows you to specify the columns you want to retrieve, filter data based on specific conditions, sort the result set, and perform aggregate functions. Here’s an example:
SELECT employee_id, first_name, last_name
FROM employees
WHERE department_id = 100;
In this example, we are selecting the employeeid, firstname, and lastname columns from the employees table, filtering the result set to only include records where the departmentid is 100.
INSERT Statement:
The INSERT statement is used to add new data to a table in the database. It allows you to specify the columns you want to insert data into and provide the values for those columns. Here’s an example:
INSERT INTO employees (employee_id, first_name, last_name)
VALUES (1001, 'John', 'Doe');
In this example, we are inserting a new record into the employees table with the employeeid, firstname, and last_name values specified.
UPDATE Statement:
The UPDATE statement is used to modify existing data in a table. It allows you to specify the columns you want to update, provide new values for those columns, and apply conditions to filter the rows to be updated. Here’s an example:
UPDATE employees
SET first_name = 'Jane'
WHERE employee_id = 1001;
In this example, we are updating the firstname column of the employees table for the record where the employeeid is 1001, changing it from ‘John’ to ‘Jane’.
DELETE Statement:
The DELETE statement is used to remove data from a table in the database. It allows you to specify conditions to filter the rows to be deleted. Here’s an example:
DELETE FROM employees
WHERE employee_id = 1001;
In this example, we are deleting the record from the employees table where the employee_id is 1001.
Conclusion:
Understanding and mastering CRUD operations in Oracle is essential for anyone working with databases. By knowing how to create, read, update, and delete data, you can effectively manage the information stored in the database. In this article, we covered the basics of each CRUD operation with examples to help you get started on your journey to becoming an Oracle database expert.