SQL Language Reference

This section provides comprehensive documentation for the SQL Server Transact-SQL (T-SQL) language. Discover the syntax, functions, and statements used to interact with and manage SQL Server databases.

Core Concepts

Understanding the fundamental building blocks of T-SQL is crucial for effective database development. Explore topics such as:

Data Types: Learn about the various data types available in SQL Server and their appropriate uses.
Operators: A guide to arithmetic, comparison, logical, and bitwise operators.
Expressions: How to construct expressions that evaluate to a single value.
Constraints: Defining rules to maintain data integrity, such as PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK, and DEFAULT.

Statements and Commands

Master the essential T-SQL statements for data manipulation, definition, and control.

Data Manipulation Language (DML)

SELECT: Retrieve data from one or more tables.
INSERT: Add new rows of data into a table.
UPDATE: Modify existing data in a table.
DELETE: Remove rows from a table.
MERGE: Perform INSERT, UPDATE, or DELETE operations on a target table based on the results of a join with a source table.

Data Definition Language (DDL)

CREATE TABLE: Define new tables in the database.
ALTER TABLE: Modify the structure of an existing table.
DROP TABLE: Remove a table and all its data.
CREATE INDEX: Improve query performance by creating indexes.
CREATE VIEW: Define virtual tables based on the results of a stored query.

Data Control Language (DCL)

GRANT: Provide permissions to users or roles.
REVOKE: Remove permissions from users or roles.

Built-in Functions

SQL Server provides a rich set of built-in functions for various tasks:

Category	Function Name	Description
Aggregate	AVG()	Calculates the average value of a column.
Aggregate	COUNT()	Counts the number of rows or non-null values in a column.
Aggregate	MAX()	Returns the maximum value in a set of values.
Aggregate	MIN()	Returns the minimum value in a set of values.
Aggregate	SUM()	Calculates the sum of values in a numeric column.
String	CONCAT()	Concatenates strings.
String	LEN()	Returns the length of a string.
String	LOWER()	Converts a string to lowercase.
String	UPPER()	Converts a string to uppercase.
Date and Time	GETDATE()	Returns the current database system date and time.
Date and Time	DATEPART()	Returns a specified part of a date as an integer.
Mathematical	ABS()	Returns the absolute value of a numeric expression.
Mathematical	ROUND()	Rounds a numeric value.

Advanced Topics

Stored Procedures: Creating and managing reusable blocks of T-SQL code.
Triggers: Executing T-SQL code automatically in response to data modification events.
Cursors: Processing rows in a database one at a time.
Transactions: Ensuring data consistency and integrity through ACID properties.

For detailed syntax and examples of each statement and function, please navigate through the sidebar or use the search functionality.