Tag: T-SQL

I heard someone say recently that you can’t change a primary key value in a row. That’s not the case, so I decided to show a quick proof of that.

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 set up a simple table with some data.

CREATE TABLE PKChangeTest (

ImportantNumber VARCHAR(20) NOT NULL CONSTRAINT PKChangeTestPK PRIMARY KEY

, CustomerName VARCHAR(50)

, StatusValue INT)

GO

INSERT dbo.PKChangeTest
   (ImportantNumber, CustomerName, StatusValue)

VALUES
   ('1234567', 'Steve', 1)

,  ('2345678', 'Andy', 1)

,  ('3456789', 'Brian', 1)

,  ('1235667', 'Leon', 1)

,  ('1265567', 'Dave', 1)

,  ('9914567', 'Bill', 1)

GO

If I look at this table, I have some unique numbers making up the PKs. If I select from the table, I can see the data.

Now, let’s change some data. I’ll change the PK values with a few statements. Then I’ll select from the table, and we will see things changed.

The ImportantNumber for both Bill and Steve have changed. These are PK modifications.

We can change a PK value. These are not set in stone once inserted.

SQL New Blogger

This is a short look at something that’s a myth among some people. When I heard someone say this, I knew I needed to prove this. The scenario took just about 5 minutes to set up (even without AI), and then it was another 10 minutes to structure and write this post.  I actually have 2 more ideas from this on things I can show to prove how PKs work and are malleable.

You can do the same thing. When you wonder about something, or hear something that isn’t true from others, prove it. And blog about it.

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.

We recently published an article on CHOOSE at SQL Server Central. I thought it was a good intro, but as someone noted in the comments, how do you use CHOOSE? Do you have to hard code choices?

This post shows you don’t.

Another post for me that is simple and hopefully serves as an example for people trying to get blogging as #SQLNewBloggers.

A Scenario

I have a table that contains some data. In this case, about beer. I like beer, and this was a fun little demo. I’m not recreating the DDL because, well, you might like different beers.

In any case, this is simple to set up.

If I wanted to choose some data from this table based on an index, I could do something like this. This code populates the first index in choose with beers and the second with brewers. CHOOSE is 1-based indexing.

DECLARE @i INT = 1;
SELECT
   CHOOSE (@i, beername, brewer)
FROM dbo.Beer AS b2;

This returns me the beers.

If I changed the value to 2, I get brewers. I show both below.

How would I use this? Maybe a user is asking to edit either a home or shipping address. I can index these by returning the column data as index 1 or 2, and linking the user suggestion to the index. They choose home, we pass in 1. If we qualify the query with a WHERE clause to one customer, they get just their data to edit.

I could even do something silly, like getting values from different places. For example, here I’ll use string_split on a value.

DECLARE @i INT = 2;
DECLARE @s VARCHAR(20) = 'Vodka,Tequila,Bourbon'

; WITH a (value)
AS
(SELECT a.value FROM STRING_SPLIT(@s, ',', 1) AS a
  WHERE a.ordinal = 1
),
  b (value)
AS
(SELECT a.value FROM STRING_SPLIT(@s, ',', 1) AS a
  WHERE a.ordinal = 2
),
  c (value)
AS
(SELECT a.value FROM STRING_SPLIT(@s, ',', 1) AS a
  WHERE a.ordinal = 3
) 
SELECT
   CHOOSE (@i, a.value, b.value, c.value)
  FROM a, b, c

This is silly, but it does return an acceptable answer.

I don’t know that there are many places that I’d use CHOOSE, but as I play with it, I can see that it could be a handy tool at times with a little creativity.

SQL New Blogger

This post took me about 15 minutes to write after I saw a comment. I set up a scenario and posted a reply, then took that code to structure this post. The STRING_SPLIT piece was the longest, as I had to futz with code, but I show some use of a new feature and how I might incorporate this into an application.

You could write your own creative blog on this, probably in 30 minutes or less. I bet you’d get asked about this in an interview as it’s kind of funny.