Tag: SQLNewBlogger

I’ve never used the FETCH or OFFSET commands for pagination, but I have heard of them. I ran across them recently and decided to experiment a bit.

One note: I have seen notes about performance, so before you do more than experiment, read about the issues (SQLPerformance, Use the Index, Luke)

This is part of the ORDER BY clause, and this allows you to skip a number of rows and then also only get a certain number of rows in the result set. The basic syntax is:

… ORDER BY XX
 OFFSET YYY ROWS
FETCH {FIRST|NEXT} ZZZ ROWS

This means, if I have a query link this one, I get the first ten rows with a 0 offset.

SELECT 
  f.FlightDate, f.DepartureAirport, f.DestinationAirport
  FROM dbo.Flight AS f
  ORDER BY f.FlightDate
  OFFSET 0 ROWS
  FETCH FIRST 10 ROWS ONLY

If I want the next 10, I can change the offset to 10.

SELECT 
  f.FlightDate, f.DepartureAirport, f.DestinationAirport
  FROM dbo.Flight AS f
  ORDER BY f.FlightDate
  OFFSET 10 ROWS
  FETCH NEXT 10 ROWS ONLY

The OFFSET must proceed the FETCH, and OFFSET can be 0. If I want to make this page, I need to ensure I change the value for OFFSET to skip the rows already returned. I can use variables here:

DECLARE @offset INT = 2
, @fetch INT = 4;

SELECT 
  f.FlightDate, f.DepartureAirport, f.DestinationAirport
  FROM dbo.Flight AS f
  ORDER BY f.FlightDate
  OFFSET @offset ROWS
  FETCH FIRST @fetch ROWS ONLY

This gets me the 3rd through 6th rows in my dataset. I’ve included a vertical partition here to let me test without having to remember which rows are which.

This is a really basic look at the native way for paging through data, though beware the entire query runs and then the engine filters out data. This may or not be a big performance issues, but on large amounts of data it will be.

SQLNewBlogger

A quick look at a feature I ran across. I needed to test code for someone and verify it works, which means I needed to take 10 minutes and try a few queries. This entire post took my about 15 minutes to write and it gives me ideas for other posts.

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

I recently ran across some people discussing how to log some information in a script. One person was using PRINT, which I often use for quick checks, but someone else noted the RAISERROR works well, and you can customize messages.

For example, I can have this type of script:

DECLARE @d VARCHAR(20);
-- do stuff
SELECT @d = CAST( SYSDATETIME() AS VARCHAR(20));

RAISERROR('%s - something happened at this time', 0, 1, @d)

This allows me to add information into an error message. I can certainly construct @d with other stuff and then use that in PRINT, but I could get out of order messages. If  I add NOWAIT, I can ensure my messages get returned immediately.

There are lots of options with RAISERROR, which I still use in place of THROW at times. While I like THROW, I think it doesn’t always give me the options I want for error handling, such as logging to the Windows lots.

SQL NewBlogger

When I saw this, I realized that I didn’t know, or remember, some of the ins and outs of RAISERROR, so I spent a few minutes looking through docs and playing with the code. I then wrote this quick post to help me remember a bit more.

Short and quick is a good way to structure posts. I didn’t walk about all the options or ways I can use things. I’ll do some of that in another post.