Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 11: Writing Scripts and Batches
Using Batches to Establish Precedence
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Note that, if you DROP an object, you may want to place the DROP in its own batch or at
least with a batch of other DROP statements. Why? Well, if you’re going to later create an
object with the same name, the CREATE will fail during the parsing of your batch unless
the DROP has already happened. That means you need to run the DROP in a separate and
prior batch so it will be complete when the batch with the CREATE statement executes.
Perhaps the most likely scenario for using batches is when precedence is required — that is, you need
one task to be completely done before the next task starts. Most of the time, SQL Server deals with this
kind of situation just fine — the first statement in the script is the first executed, and the second statement
in the script can rely on the server being in the proper state when the second statement runs. There are
times, however, when SQL Server can’t resolve this kind of issue.
Let’s take the example of creating a database together with some tables:
USE master;
CREATE DATABASE Test;
CREATE TABLE TestTable
(
col1 int,
col2 int
);
Execute this and, at first, it appears that everything has gone well:
Command(s) completed successfully.
However, things are not as they seem — check out the INFORMATION_SCHEMA in the Test database:
USE Test;
SELECT TABLE_CATALOG
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = ‘TestTable’;
And you'll notice something is missing:
TABLE_CATALOG
--------------------
AdventureWorks2008
(1 row(s) affected)
Hey! Why was the table created in the wrong database? The answer lies in what database was current
when we ran the CREATE TABLE statement. In my case, it happened to be the master database, so that’s
where my table was created.
Note that you may have been somewhere other than the master database when you ran this, so you may
get a different result. That’s kind of the point though — you could be in pretty much any database.
That’s why making use of the USE statement is so important.