TSQL in ORACLE

This site will primarily focus on T-SQL used with Microsoft SQL Server. Most examples are for Microsoft SQL Server 2005, but most will work for earlier and later editions. The site will be updated as new editions of SQL Server are released. The Pages that aren't not linked in the navigation bar have not yet been completed. All Pages should be completed by the end of June 2008. For those just starting with SQL Server, some definitions are provided below:
SQL stands for Structured Query Language. It is most often pronounced "sequel" or sometimes pronounced by spelling out the letters "S-Q-L". SQL is a query language that is used to interact and perform tasks with relation databases. This language was originally developed by IBM in the 1970s.
T-SQL (Transact SQL) is a proprietary SQL extension used by Microsoft SQL Server and Sybase SQL Server. T-SQL adds extensions for procedural programming.
Flow control
Keywords for flow control in Transact-SQL include BEGIN and END, BREAK, CONTINUE, GOTO, IF and ELSE, RETURN, WAITFOR, and WHILE.
IF and ELSE allow conditional execution. This batch statement will print "weekend" if the current date is a weekend day, or "weekday" if the current date is a weekday.
IF DATEPART(dw, GETDATE()) = 7 OR DATEPART(dw, GETDATE()) = 1 PRINT 'It is the weekend.'ELSE PRINT 'It is a weekday.'
BEGIN and END mark a block of statements. If more than one statement is to be controlled by the conditional in the example above, we can use BEGIN and END like this:
IF DATEPART(dw, GETDATE()) = 7 OR DATEPART(dw, GETDATE()) = 1BEGIN PRINT 'It is the weekend.' PRINT 'Get some rest!'ENDELSEBEGIN PRINT 'It is a weekday.' PRINT 'Get to work!'END
WAITFOR will wait for a given amount of time, or until a particular time of day. The statement can be used for delays or to block execution until the set time.
RETURN is used to immediately return from a stored procedure or function.
BREAK ends the enclosing WHILE loop, while CONTINUE causes the next iteration of the loop to execute. An example of a WHILE loop is given below.
Local variables
Local variables are so named because they're local to the script executing them. Transact SQL doesn't support user-defined global variables.
DECLARE will declare a variable, giving it a name and a type. The SET statement can be used to provide a value, and the variable may be used in a statement by referencing its name.
This script declares a variable as an integer, initializes it, then uses WHILE to execute a loop.
DECLARE @Counter INT
SET @Counter = 10
WHILE @Counter > 0
BEGIN
PRINT 'The count is ' + CONVERT(VARCHAR(10), @Counter)
SET @Counter = @Counter - 1
END
The body of the loop will print a message including the value of the variable, and then decrement the counter.
A variable can be initialized as the result of a statement, like this:
DECLARE @ArticleCount INT
SELECT @ArticleCount = COUNT(*) FROM Articles
INSERT INTO SizeLog (SampleTime, ArticleCount) VALUES (GETDATE(), @ArticleCount)
which will get the count of rows in the Articles table, then insert a row including that count and the current clock time into the SizeLog table.
Changes to DELETE and UPDATE statements
In Transact-SQL, both the DELETE and UPDATE statements allow a FROM clause to be added, which allows joins to be included.
This example deletes all users who have been flagged with the 'Idle' flag.
DELETE users
FROM users AS u
JOIN user_flags AS f
ON u.id=f.id
WHERE f.name = 'Idle'
BULK INSERT
BULK INSERT is a Transact-SQL statement that implements a bulk data-loading process, inserting multiple rows into a table, reading data from an external sequential file. Use of BULK INSERT results in better performance than processes that issue individual INSERT statements for each row to be added.