SQL Documentation FAQ

SQL (Structured Query Language) is a standard language for managing and manipulating databases. It's used to communicate with a database. SQL is used to perform tasks such as updating data, deleting data, and querying data.

The main SQL commands fall into categories:

• DDL (Data Definition Language): CREATE, ALTER, DROP
• DML (Data Manipulation Language): SELECT, INSERT, UPDATE, DELETE
• DCL (Data Control Language): GRANT, REVOKE
• TCL (Transaction Control Language): COMMIT, ROLLBACK, SAVEPOINT

A database schema is the blueprint or structure of a database. It defines how data is organized and how the relations among them are associated. It includes tables, columns, data types, primary keys, foreign keys, and other constraints.

Microsoft SQL Server is a relational database management system developed by Microsoft. It's a popular choice for enterprise-level applications, offering a wide range of features for data storage, retrieval, and management.

Stored procedures are a set of SQL statements and procedural logic that are stored in the database. They can be executed by calling the procedure name, offering benefits like improved performance, security, and reusability.

Example:

CREATE PROCEDURE GetCustomerOrders
                        @CustomerID INT
                    AS
                    BEGIN
                        SELECT OrderID, OrderDate, TotalAmount
                        FROM Orders
                        WHERE CustomerID = @CustomerID;
                    END;

Triggers are special stored procedures that automatically execute in response to certain events on a particular table or view in a database. They are often used to enforce business rules, maintain data integrity, or audit data changes.

T-SQL (Transact-SQL) is Microsoft's proprietary extension to SQL used by Microsoft SQL Server. It adds procedural programming, local variables, various support functions for data manipulation, and enhancements for creating and managing database objects.

Optimizing SQL queries involves several techniques:

• Indexing: Properly indexing tables to speed up data retrieval.
• SELECT specific columns: Avoid `SELECT *`.
• WHERE clause: Filter data efficiently early in the query execution.
• Query analysis: Use execution plans to identify bottlenecks.
• Minimize JOINs: Use appropriate JOIN types and reduce unnecessary ones.
• Avoid functions in WHERE clauses: These can prevent index usage.

An index is a data structure that improves the speed of data retrieval operations on a database table. It works much like an index in the back of a book, allowing the database to find rows more quickly without scanning the entire table.

Normalization is a database design technique used to organize data to reduce redundancy and improve data integrity. It involves dividing larger tables into smaller, less redundant tables and defining relationships between them.

A transaction is a sequence of database operations performed as a single logical unit of work. Transactions are atomic, consistent, isolated, and durable (ACID), ensuring data integrity even in the event of errors or system failures.