When coming from a programming background, it’s natural to want to frame conditional operations within the familiar if.. else constructs. This happens in a lot of SQL code I have worked with (and I used to be a contributor also). The technique below is based on a common scenario. Say you want to insert new [...]
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DROP INDEX SYNTAX
Here is the syntax needed in order to drop a single index: USE YourDatabaseName; DROP INDEX IX_Product_1 ON dbo.Product; You can also drop multiple indexes within a single transaction: USE YourDatabaseName; DROP INDEX IX_Product_1 ON dbo.Product, IX_Customer_1 ON dbo.Customer; Permissions The permissions needed to drop an index are alter permissions to the table. This is [...]
SET TRANSACTION ISOLATION LEVEL
This statement is used to set the isolation level for either a connection or a stored procedure. The most typical use I’ve seen is at the top of a stored procedure in order to avoid locking and deadlocks. This is a cleaner alternative to using WITH (NOLOCK) hints on tables. If you set the isolation [...]
How to Create a Type2 SCD (Slowly Changing Dimension)
This article could just as well be called creating a historical snapshot table. This type of table is also referenced as a dimension depending on what kind of data repository it’s located in. Personally, I prefer to keep a historical snapshot table in a normalized data store that contains history. This normalized data store is [...]
Using DBCC CHECKIDENT to Reseed a Table After Delete
I imagine you are just looking for simple syntax in order to reseed the identity column of a table you just deleted from. Here is the quick version: DBCC CHECKIDENT(‘##reseed_example’, RESEED, @max_seed) And here is an extended example: — populate a table with identity SELECT ID = IDENTITY(int,1,1) ,name INTO ##reseed_example FROM dbo.sysobjects — delete [...]
CROSS APPLY Explained
My first introduction to the APPLY operator was using the DMVs. For quite a while after first being introduced, I didn’t understand it or see a use for it. While it is undeniable that it is has some required uses when dealing with table valued functions, it’s other uses evaded me for a while. Luckily, [...]
Indexed Views
To explain what an indexed view is, let’s first look at what constitutes a view. A view may sound like a fancy elaborate thing, however all it is, is a saved SELECT statement, nothing else. It is not explicitly compiled, nor does it contain any data. When you select from a view, it goes to [...]
Auto Update Statistics & Auto Create Statistics
The ability to create and update statistics is a crucial liberty for the query optimizer. The optimizer needs to know how it is going to query underlying tables, and when the statistics do not match the data, it is very probable that it will choose a non-efficient method for querying. I’ve seen and heard a [...]
Using DBCC UPDATEUSAGE
When DBCC UpdateUsage is run, page and row counts are updated. When this information is incorrect, it can give incorrect reports for how much space is used by tables and indexes. The most likely cause for incorrect usage stats is when a database is upgraded to a new compatibility level of SQL Server (i.e. 2000 [...]
Using IDENTITY_INSERT
The only way to insert values into a field that is defined as an “IDENTITY” (or autonumber) field, is to set the IDENTITY_INSERT option to “ON” prior to inserting data into the table. To illustrate, let’s create a table that has an identity column defined. — Create table with identity column CREATE TABLE MyOrders ( [...]
