There is a SET command in SQL Server that changes how much data is returned from some fields. This short post shows what I learned about the SET TEXTSIZE command.
Another post for me that is simple and hopefully serves as an example for people trying to get blogging as #SQLNewBloggers.
The Scenario
Let’s start with a little code. I actually created a table that looks like this:
CREATE TABLE [dbo].[Beer] ( [BeerID] [int] NOT NULL IDENTITY(1, 1), [BeerName] [varchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, [brewer] [varchar] (20) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, [beerdescription] [varchar] (max) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] GO
I added data so that I have something in here:
INSERT INTO dbo.Beer (BeerName, brewer, beerdescription) VALUES (1, 'Becks', 'Interbrew', 'Beck''s is a German-style pilsner beer known for its golden color, full-bodied taste, and a crisp, clean finish with floral and fruity hop aromas, brewed according to the German purity law') ,(2, 'Fat Tire', 'New Belgium Toasty malt, gentle sweetness, flash of fresh hop bitterness. The malt and hops are perfectly balanced.') ,(3, 'Mac n Jacks', 'Mac & Jack''s Brewery', 'This beer erupts with a floral, hoppy taste, followed by a well rounded malty middle, finishing with a nicely organic hop flavor. Locally sourced two row grain and a blend of specialty malts give our amber its rich taste.') ,(4, 'Alaskan Amber', 'Alaskan Brewing', 'Alaskan Brewing Amber Ale is an "alt" style beer, meaning it''s fermented slowly and at colder temperatures, resulting in a well-balanced, richly malty, and long-lasting flavor profile with a clean, pleasing aftertaste.') ,(8, 'Kirin', 'Kirin Brewing', 'Kirin Ichiban is a Lager-type beer, which means it is fermented at low temperatures and offers a light and refreshing texture with a smooth and balanced flavor.')
Now, let’s see what this setting does.
SET TEXTSIZE
This command changes the behavior of SELECT queries and controls how much data is returned in bytes. The setting is the command with an integer after it. The max value is 2GB.
I’ll run a normal query, then I’ll set a smaller size and repeat the query. Notice how the results differ below. I get less data in the second query.
What this setting does is limit the number of bytes from some fields. I only have 20 characters from each description.
Let’s do one more query. I’ll lower the value to 5.
Note that while the description is very low, the name and brewer are not cut off.
The explanation is that this works on the max types: varchar(max), nvarchar(max), varvinary(max), text, ntext, and image. Non-max fields aren’t affected.
Also note that the default setting from the SQL Native Client and ODBC driver is –1, for unlimited data. That explains why I haven’t noticed this as I’m often using an app that uses one of those. IF you set this to 0, then it defaults to 4KB.
A nice way to prevent apps from grabbing tons of data unless they need it, though you’d certainly need to help users understand why they weren’t getting all the data expected. I think long fields (or image/audio/etc. data) would need a “get more” or “get all” item in software to reset this and return the full value in the table.
SQL New Blogger
This was a function I ran across, whose purpose I had no idea about. I read it, experimented, and in about 30 minutes had put together this demo and post. Easy to do and quick.
I learned something, and I’m sharing this with potential employers. You could as well, with a little effort.