SQL Server BEGIN/END vs BEGIN TRANS/COMMIT/ROLLBACK

I have been trying to find info on the web about the differences between t开发者_如何学Gohese statements, and it seems to me they are identical but I can't find confirmation of that or any kind of comparison between the two.

What is the difference between doing this:

BEGIN
    -- Some update, insert, set statements
END

and doing this

BEGIN TRANS
    -- Some update, insert, set statements
COMMIT TRANS

?

Note that there is only the need to rollback in the case of some exception or timeout or other general failure, there would not be a conditional reason to rollback.

BEGIN and END deal with code blocks. They are similar to the curly braces you see in many languages:

if (somethingIsTrue)
{ // like BEGIN
    // do something here
} // like END

In SQL, this is:

if somethingIsTrue
BEGIN
    -- do something here
END

BEGIN TRAN, COMMIT, and ROLLBACK begin and end transactions. They do not specify a new block of code; they only mark the transaction boundaries.

Note that you can write a BEGIN TRAN and COMMIT in separate blocks of code. For example, if you want code to be part of a transaction, but you don't want to start a new one if the code is already in a transaction, you can do something like this:

declare @TranStarted bit = 0
if @@trancount = 0
begin
    set @TranStarted = 1
    begin tran
end

-- ... do work ...

if @TranStarted = 1
begin
    commit
    set @TranStarted = 0
end

The regular BEGIN and END are not used for transactions. Instead, they are just for indicating that some block of code is a single unit, much like braces {} in C#/C++/Java.

If you have an IF statement or a WHILE loop that does 10 things, you need to enclose them in BEGIN/END so that SQL Server knows that that whole list of 10 statements should be executed as a part of that condition.

These 2 statements are entirely different.

BEGIN..END mark a block of code, eg in an if statement

IF @something = 1
BEGIN
  -- Do something when @something is equal to 1
END

BEGIN TRANS..COMMIT TRANS wrap the enclosing block in a transaction, and depending on server settings will rollback the transaction if an error occurs.

It should be mentioned, that there is a Begin; in PostgreSQL, that also initiates a transaction block, which at first confused me.

http://www.postgresql.org/docs/9.0/static/sql-begin.html

"BEGIN initiates a transaction block, that is, all statements after a BEGIN command will be executed in a single transaction until an explicit COMMIT or ROLLBACK is given. By default (without BEGIN), PostgreSQL executes transactions in "autocommit" mode, that is, each statement is executed in its own transaction and a commit is implicitly performed at the end of the statement (if execution was successful, otherwise a rollback is done)."

I have not seen END TRANS :)

i think we use END only for BEGIN keyword not for BEGIN trans we use commit or rollback for BEGIN trans