In Oracle Database, you can perform basic CRUD (Create, Read, Update, Delete) operations using SQL commands. Here's a brief overview of how to execute these operations:
Please note, this is also called Data Manipulation Language (DML).
1. Insert:-
To add new records to a table, you use the INSERT statement. The syntax is as follows:-
INSERT INTO table_name (column1, column2, ...)
VALUES (value1, value2, ...);
2. Update:-
To modify existing records in a table, you use the UPDATE statement. The syntax is as follows:-
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
3. Delete:-
To remove records from a table, you use the DELETE statement. The syntax is as follows:-
DELETE FROM table_name
WHERE condition;
Here, the condition specifies which records to delete. If you omit the WHERE clause, all records in the table will be deleted.
Example:-
Let's assume we have a table named employees with columns employee_id, first_name, last_name, and salary. Here's how you can perform CRUD operations:-
1. Insert:-
INSERT INTO employees (employee_id, first_name, last_name, salary)
VALUES (1, 'John', 'Doe', 50000);
2. Update:-
UPDATE employees
SET salary = 55000
WHERE employee_id = 1;
3. Delete:-
DELETE FROM employees
WHERE employee_id = 1;
These are basic examples of how to perform CRUD operations in Oracle Database. Make sure to replace table_name, column_name, and condition with appropriate values based on your database schema and requirements. Additionally, always be cautious when executing DELETE statements to avoid unintentional data loss.
Here are five frequently asked questions (FAQs) about performing CRUD operations (Create, Read, Update, Delete) in Oracle Database:-
1. Can I insert multiple rows into a table with a single INSERT statement in Oracle?
- Yes, you can insert multiple rows into a table with a single INSERT statement by providing multiple sets of values separated by commas in the VALUES clause. For example:-
INSERT INTO table_name (column1, column2, ...)
VALUES (value1_1, value1_2, ...),
(value2_1, value2_2, ...),
...
2. How do I perform a bulk update in Oracle to update multiple records efficiently?
- You can perform a bulk update in Oracle using the UPDATE statement with the WHERE clause to specify the conditions for updating multiple records. Additionally, you can use the MERGE statement for more complex update scenarios involving data from multiple sources.
3. What is the difference between DELETE and TRUNCATE in Oracle?
- The DELETE statement is used to remove specific records from a table based on specified conditions, while the TRUNCATE statement is used to remove all records from a table, effectively resetting the table's data. Unlike DELETE, TRUNCATE is a DDL (Data Definition Language) statement and is faster because it does not generate undo logs.
4. Can I rollback changes made by INSERT, UPDATE, or DELETE statements in Oracle?
- Yes, you can rollback changes made by INSERT, UPDATE, or DELETE statements by issuing the ROLLBACK statement before committing the transaction. This reverts all changes made within the current transaction to the state they were in before the transaction began.
5. Is it possible to perform CRUD operations across multiple tables in a single transaction in Oracle?
- Yes, you can perform CRUD operations across multiple tables in a single transaction in Oracle by using transaction control statements such as COMMIT and ROLLBACK. By enclosing multiple SQL statements within a transaction, you ensure that either all changes are committed together or none of them are, maintaining data integrity.
