TSQL SYNTAX HELP PLEASE!!!!

Question

TSQL SYNTAX HELP PLEASE!!!!

CDAnkrum

SSC Enthusiast

Points: 113
More actions
January 24, 2016 at 7:06 pm

#307279

Hello Gurus...
I am new to SQL and trying to teach myself to do more than just query.
I have a Stored Procedure that I am attempting to understand and need some help. Can someone explain to me IN ENGLISH what this statement is doing??
IF (ISNULL(@phrase_type, ' ') = ' ')
(I know that the statement is testing whether the variable @phrase_type is null, but what does the " ,' ') = ' ')" do???
And go....
(Thanks in advance!!)

Viewing 6 posts - 1 through 5 (of 5 total)

You must be logged in to reply to this topic. Login to reply

pietlinden SSC Guru Points: 63428 More actions · Answer 1

You owe it to yourself to make friends with Books On Line ( the help file for SQL Server ). Hidden very carefully under the F1 key. Also, when you're trying to understand what something like this does, take it apart and add a layer at a time.

Run this:

SELECT ISNULL(Null,'This is Null')

Then add the stuff outside of it. And keep building outward when you understand each piece. it's the only way to get your head around TSQL. Practice, practice, practice. And don't be afraid to experiment.

Igor Micev SSC-Dedicated Points: 33109 More actions · Answer 2

Tons of materials. As appointed by pietlinden, you can use other sources on web like for example the following 10 lessons on http://sqlmag.com/t-sql/t-sql-101-lesson-1

It's important that you start with one book/site/teaching source etc, and go with it until finishing a cycle.

Igor Micev,My blog: www.igormicev.com

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 3

IT2012 (1/24/2016)
(I know that the statement is testing whether the variable @phrase_type is null

That's not what it's doing. It's part of what it will do, but not all it will do.

Break it up into pieces. You have an IF with a condition and an expression in that condition. So there are two things you need to look at separately.

First, the expression

ISNULL(@phrase_type, ' ')

Once you're happy with what that does, then you have the IF with it's condition

IF (<expression listed above> = ' ')

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

CDAnkrum SSC Enthusiast Points: 113 More actions · Answer 4

Thank you for your responses. They are very much appreciated!!!

ScottPletcher SSC Guru Points: 100948 More actions · Answer 5

Here's the clear version of the code:

IF (@phrase_type IS NULL OR @phrase_type = ' ')

Instead, the original code uses:

IF (ISNULL(@phrase_type, ' ') = ' ')

The ISNULL(<value1>, <value2>) will replace a NULL value1 with value2, in this case ' '. If value1 is not null, it will return value1. With some review of the code, you can see that functionally it's the same as the code above, albeit less clear.

SQL DBA,SQL Server MVP(07, 08, 09) A socialist is someone who will give you the shirt off *someone else's* back.