Substring comprehension

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Substring comprehension

dcawvive

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October 31, 2009 at 1:20 pm

#211586

Comments posted to this topic are about the item Substring comprehension

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ShilpaSunil SSC-Addicted Points: 445 More actions · Answer 1

Refer this link

http://www.ianywhere.com/developer/product_manuals/sqlanywhere/0902/en/html/dbrfen9/00000293.htm

davoscollective SSCertifiable Points: 6355 More actions · Answer 2

Took a guess and got it wrong, but...

Ran this on 2005 and A is not actually NULL, its an empty string. Maybe its NULL on 2008?

vk-kirov SSCertifiable Points: 7686 More actions · Answer 3

The correct answer is: A is '' (empty string), B is 'Chris'.

Try this code:

declare @name varchar(12)

select @name = 'Christopher'

select case when substring(@name,15,12) is null then 'NULL' else 'NOT NULL' end as A, substring(@name,-6,12) as B

and you will see the result:

A B

-------- ------------

NOT NULL Chris

(1 row(s) affected)

Despite what is shown in 2008 BOL

Maybe the author of the question uses some "secret special" BOL 😉

I use the following link: http://msdn.microsoft.com/en-us/library/ms187748.aspx, and what I see there:

SUBSTRING ( value_expression ,start_expression , length_expression )
...
If length_expression is negative, an error is generated and the statement is terminated.

So, length_expression cannot be negative, but the "-6" from the question is start_expression.

the code ... does not return the whole value expression when the sum of the start and length values are greater than the length of the variable

Just a little detail from BOL:

the whole value expression beginning at start_expression is returned

😉

honza.mf SSCertifiable Points: 5519 More actions · Answer 4

Just a little mistake, empty string and null.

But to tell the truth, I was confused, because I know the first expression returns empty string and not a null...

See, understand, learn, try, use efficient
© Dr.Plch

Toby White SSCertifiable Points: 6187 More actions · Answer 5

Even though A is empty string versus Null the answer is still obvious given that it is multiple choice. In other words it was obvious that the author had just made a mistake between empty/null since options A and C were so far off.

BudaCli Hall of Fame Points: 3384 More actions · Answer 6

I chose the one closest to the answer and I seem to have got it right. Hihahhhhh

What you don't know won't hurt you but what you know will make you plan to know better

premkuttan SSCommitted Points: 1934 More actions · Answer 7

Can some one explains how it returns 'chris' when the start value is -6 and length is 12.

VM-723206 SSCrazy Points: 2964 More actions · Answer 8

VM-723206

SSCrazy

Points: 2964

November 3, 2009 at 8:04 am

#1074280

sorry, wrong post..

mark.ross Valued Member Points: 53 More actions · Answer 9

If you think of it sort of as a number line, the name "Christopher" would occupy spots 1 thru 11 of the line. The expression is askiing you to look at spots -6 thru 5. This is 12 spots because of the number zero. The first 7 spots (-6 thru 0) we're asked to look at don't correspond to any characters in the name and don't return any characters. But the last 5 spots correspond to spots 1 thru 5 of the number line and those spots are occupied by the characters "Chris".

This is perhaps a clumsy example, but it seems to work.

fzaynoun Valued Member Points: 52 More actions · Answer 10

A empty not null. Substring returns null only if expression is null.

Ronzo Hall of Fame Points: 3917 More actions · Answer 11

Toby White (11/2/2009)
Even though A is empty string versus Null the answer is still obvious given that it is multiple choice. In other words it was obvious that the author had just made a mistake between empty/null since options A and C were so far off.

So...

Always assume that there is a right answer, and if none of the above is not shown, try and figure out which answer would be right assuming the author made a mistake.

Don't like this logic at all. It may result in your passing the test, but it requires you to try and figure out what the author "meant" the answers to be.

I used logic that went like this... if you know two of the answers are wrong, go with the one that might be right (i.e. error). Of course my "logic" failed and yours succeeded, this time. 😀

Have Fun!
Ronzo

TomThomson SSC Guru Points: 104773 More actions · Answer 12

As some previous commenters did, I got this right by guessing what the questioner had got wrong.

Tom

Frédéric van der Plancke SSC Enthusiast Points: 198 More actions · Answer 13

Toby White (11/2/2009)
Even though A is empty string versus Null the answer is still obvious given that it is multiple choice. In other words it was obvious that the author had just made a mistake between empty/null since options A and C were so far off.

Except that A is not so far off. I thought along this line: this first select returns the empty string, I don't know what the second one does, but no answer has "this first select returns the empty string", so the only compatible answer is A: error.

Not nice.