Transact-SQL Overview

Transact-SQL is central to the use of Microsoft® SQL Server™. All applications that communicate with SQL Server do so by sending Transact-SQL statements to the server, regardless of the application's user interface.

Transact-SQL is generated from many kinds of applications, including the following.

General office productivity applications.
Applications that use a graphical user interface (GUI) to allow users to select the tables and columns from which they want to see data.
Applications that use general language sentences to determine what data a user wants to view.
Line of business applications that store data in SQL Server databases - including both applications from other vendors and applications written in-house.
Transact-SQL scripts that run using utilities such as OSQL.

This table contains the more important clauses and functions of Transact-SQL.

Clause/Function	Description
SELECT Clause	Specifies the columns to be returned by the query.
FROM Clause	Specifies the table(s) from which to retrieve rows. The FROM clause is required except when the select list contains only constants, variables, and arithmetic expressions (no column names).
WHERE Clause	Specifies a search condition to restrict the rows returned.
GROUP BY Clause	Specifies the groups into which output rows are to be placed and, if aggregate functions are included in the SELECT clause <select list>, calculates a summary value for each group. When GROUP BY is specified, either each column in any non-aggregate expression in the select list should be included in the GROUP BY list, or the GROUP BY expression must match exactly the select list expression.
AND Function	Combines two Boolean expressions and returns TRUE when both expressions are TRUE. Used when there are more than one logical operator in a statement - AND operators are evaluated first. Use parentheses to change the order of evaluation.
OR Function	Combines two conditions. Used when there are more than one logical operator is in a statement - OR operators are evaluated after AND operators. Use parentheses to change the order of evaluation.
LIKE Function	Determines whether or not a given character string matches a specified pattern. A pattern can include regular characters and wildcard search characters. During pattern matching, regular characters must match exactly the characters specified in the character string - wildcard characters, however, can be matched with arbitrary fragments of the character string. Using wildcard search characters makes the LIKE operator more flexible than using the = and != string comparison operators. If any argument is not of character string data type, Microsoft® SQL Server™ converts them to character string data type, if possible.
COUNT Field Function	Returns the number of items in a group.
DATADIFF Field Function	Returns the number of date and time boundaries crossed between two specified dates.
MAX Field Function	Returns the maximum value in the expression.
MIN Field Function	Returns the minimum value in the expression.

Further Reference

Reference the following web site for further information about including other functions in the Profile.