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Topics

Introduction to SQL

What is SQL?SQL History SQL Standards SQL vs NoSQL SQL Database Management Systems

SQL Basics

SQL Syntax SQL Comments SQL Data Types SQL Operators SQL Expressions SQL Literals SQL Identifiers SQL Keywords SQL Case Sensitivity

SQL Database Fundamentals

Database Concepts Tables and Fields Primary Keys Foreign Keys Indexes Constraints Normalization Denormalization SQL Schema Design

SQL Data Manipulation

SQL SELECT Statement SQL INSERT Statement SQL UPDATE Statement SQL DELETE Statement SQL MERGE Statement SQL Aliases SQL Wildcards SQL LIKE Operator SQL IN Operator SQL BETWEEN Operator SQL NULL Values SQL ORDER BY Clause SQL LIMIT Clause SQL OFFSET Clause

SQL Filtering and Sorting

SQL WHERE Clause SQL AND, OR, NOT Operators SQL GROUP BY Clause SQL HAVING Clause SQL DISTINCT Keyword SQL TOP Clause

SQL Joins

SQL INNER JOIN SQL LEFT JOIN SQL RIGHT JOIN SQL FULL OUTER JOIN SQL CROSS JOIN SQL Self JOIN SQL Natural JOIN SQL Multiple JOINs

SQL Functions

SQL Aggregate Functions SQL Scalar Functions SQL String Functions SQL Numeric Functions SQL Date Functions SQL Conversion Functions SQL System Functions SQL User-Defined Functions

SQL Subqueries

SQL Subquery Basics Correlated Subqueries Nested Subqueries SQL EXISTS Operator SQL ANY and ALL Operators Subqueries in SELECT Subqueries in FROM Subqueries in WHERE

SQL Views

Creating SQL Views Altering SQL Views Dropping SQL Views Updatable Views Materialized Views View Limitations

SQL Transactions

SQL Transaction Basics ACID Properties BEGIN TRANSACTION COMMIT ROLLBACK SAVEPOINT Transaction Isolation Levels

SQL Data Definition

SQL CREATE TABLE SQL ALTER TABLE SQL DROP TABLE SQL TRUNCATE TABLE SQL CREATE INDEX SQL DROP INDEX SQL CREATE DATABASE SQL ALTER DATABASE SQL DROP DATABASE

SQL Data Control

SQL GRANT SQL REVOKE SQL Roles SQL Users SQL Privileges

SQL Performance Optimization

SQL Query Optimization SQL Execution Plans SQL Index Optimization SQL Query Tuning SQL Caching SQL Partitioning

Advanced SQL Concepts

SQL Stored Procedures SQL Triggers SQL Cursors SQL Common Table Expressions SQL Window Functions SQL Pivot and Unpivot SQL JSON Operations SQL XML Operations SQL Full-Text Search

SQL Best Practices

SQL Naming Conventions SQL Code Organization SQL Error Handling SQL Security Best Practices SQL Backup and Recovery SQL Version Control

SQL COMMIT: Finalizing Database Transactions

In SQL, the COMMIT statement plays a crucial role in database transactions. It's the final step that makes changes permanent and visible to other users.

What is COMMIT?

COMMIT is a SQL command that finalizes a transaction in a relational database. When you execute a COMMIT, all changes made during the current transaction are saved and become permanent.

Purpose of COMMIT

Ensures data integrity
Makes changes visible to other database users
Releases locks on the affected data
Marks the end of a successful transaction

Basic Syntax

COMMIT;

This simple command is typically used after a series of SQL statements that modify the database.

COMMIT in Action

Here's a practical example of using COMMIT in a transaction:

BEGIN TRANSACTION;
    UPDATE accounts SET balance = balance - 100 WHERE account_id = 1234;
    UPDATE accounts SET balance = balance + 100 WHERE account_id = 5678;
COMMIT;

In this example, we're transferring $100 between two accounts. The COMMIT ensures that both updates are applied together.

COMMIT vs. ROLLBACK

While COMMIT finalizes changes, ROLLBACK discards them. If an error occurs during a transaction, you might choose to ROLLBACK instead of COMMIT.

Best Practices

Use COMMIT after logically complete operations
Avoid excessive commits, as they can impact performance
Ensure all operations in a transaction are successful before committing
Use Transaction Isolation Levels to manage concurrent access

COMMIT and ACID Properties

COMMIT is crucial for maintaining the ACID properties of database transactions, particularly Durability. It ensures that once a transaction is committed, its effects persist even in the event of system failures.

Auto-Commit Mode

Some database systems have an auto-commit mode where each individual SQL statement is automatically committed. While convenient, it can limit control over transaction boundaries.

Conclusion

Understanding and properly using COMMIT is essential for maintaining data integrity in SQL databases. It's a fundamental concept in transaction management, working hand-in-hand with BEGIN TRANSACTION and ROLLBACK to ensure reliable and consistent database operations.