Category: Syntax

Kendra Little explains the COMPRESS() function in SQL Server 2016:

One cool little feature in SQL Server 2016 is COMPRESS(). It’s a TSQL function available in all editions that shrinks down data using the GZIP algorithm (documentation).

Things to know about COMPRESS():

• Compressed data is in the VARBINARY(max) data type

• You get the data “back to normal” by  using the DECOMPRESS function – which also outputs VARBINARY(max)

• You can’t use columns of the VARBINARY(max) type in an index key column– but it may be useful to use the column as a filter in a filtered index, in some cases

COMPRESS() uses standard GZip compression, so you could use methods other than DECOMPRESS() to inflate the data—for example, bring the compressed data out to your application and use language-specific GZip libraries to decompress the data.  Read the whole thing.

Kevin Wilkie shows an example of deleting data as part of a merge operation:

The last time we were together, we learned how to use the MERGE statement when we wanted to insert rows that didn’t exist and update rows that didn’t. This time we’re going to add onto that. We’re adding the seldom used, but delightfully potent – delete rows that no longer exist in the original table.

MERGE is an enticing but dangerous piece of syntax.  It looks so nice until you realize how many bugs and oddities there are in the command.

Shane O’Neill ponders an existential problem:

So, drinking my first (of many) coffee of the day, I asked him what was wrong with it.

I have two tables. 1 with values 1,2,3 & the other with values 1,2,3,4,5. When I use delete exists, it should just delete 1,2,3 but table1 is always empty.

Hmmm, not an unreasonable assumption I suppose so I asked him for his code.

Read on for Shane’s explanation, though he doesn’t like the verbosity.  My version is, what happens in EXISTS stays in EXISTS.  It just returns a signal to the outer query saying yea or nay and the outer query does its thing accordingly.  In this case, if you want to tie results back to the delete operation, use IN (the ANSI standard way) or JOIN (typically my preferred way, given that IN can get dicey with more complex criteria).

Dennes Torres shows off four T-SQL functions releasing in SQL Server 2017:

Translate

Translate does the work of several replace functions, simplifying some queries.

The function is called ‘Translate’ because its main objective: transform one kind of information in another by doing a bunch of replaces.

For example: GeoJson and WKT are two different formats for coordinates. In GeoJson a coordinate is represented using the format ‘[137.4, 72.3]’ while in WKT a point is represented using the format ‘(137.4 72.3)’.

We would need several ‘Replace’s to transform GeoJson format in WKT format and the reverse. The ‘Translate’ function can do this easily.

I knew the first three, but Translate sneaked right past me.

Phil Factor on the IsNumeric() function:

IsNumeric() is actually answering the question ‘Can this string be converted or ‘cast’ to a numeric datatype by SQL Server?’ It is pretty good at getting this answer right but it doesn’t tell you which datatype. It also isn’t interested in such things as overflow.

This problem of IsNumeric() was solved in SQL Server 2012. There was no way of morphing IsNumeric() intro something more valuable, so Try_Cast(), Try_Parse(), and Try_Convert() were introduced. The introduction of these system functions really solve the problem, unless you are still on earlier versions than SQL Server 2012. I’ll show how to do the same thing in previous versions of SQL Server, and demonstrates one or two tricks you can do with these functions.

I’ll stick with the post-2012 version, please.

John Morehouse explains what the REVERSE function is and why it can be useful:

Recently I had a conversation with a colleague that wasn’t aware of the REVERSE function in SQL Server.  I had sent them a code snippet and they inquired as to what the purpose of the function was.  Essentially, this function that reverses any string value.

For example, the phrase:

The brown dog jumped over the lazy fox

reversed looks like this

xof yzal eht revo depmuj god nworb ehT

Read on to see a good example of when you might use REVERSE.

Shane O’Neill engages in wacky newline misadventures:

GO is a special little guy. It’s not exactly T-SQL. It’s a way of telling the SQL Server Management Studio (SSMS) to send everything before it, from the beginning of the script or the preceding GO, to the SQL Server instance.

If you read the documents, the main point to take away is…

A Transact-SQL statement cannot occupy the same line as a GO command. However, the line can contain comments.

The problem turns out to be a little trickier than you’d first imagine.  Also, after reading this post, I think it’s lunchtime…