what is the meaning of " if exists(select top 1 null from table t)"

Question

1.00/5 (1 vote)

See more:

SQL-Server-2014

what do you mean by that statement? if the condition is true, what is it going to return?
what is select top 1 null?
is it something like selecting the records even if some columns have null values also in a row to prevent the omitting of that particular row?
kindly help me with your answers.

Posted 30-Apr-15 4:39am

Sire_007

Add a Solution

Comments

Abdul Samad KP 30-Apr-15 11:08am

As Karthik said , it is just checking any rows are there in the table. There is nothing to do with null , you can use like IF EXISTS(select top 1 1 from table) also

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Karthik_Mahalingam · Answer 1 · 2015-04-30T04:55:00

Solution 1

If row(s) are present in the table it returns true else false
AFAIK no other logic behind, tested.

Posted 30-Apr-15 4:55am

Karthik_Mahalingam

Tomas Takac · Answer 2 · 2015-04-30T06:20:00

Solution 2

Karthik is right. This only checks if there are some rows in the table or not. It has the same effect as:

SQL

if exists(select * from table)

The author of that query just tried to be smart and optimize it by only selecting one row. But this is actually not needed because in both cases the query plan is exactly the same.

Posted 30-Apr-15 6:20am

Tomas Takac

Comments

Karthik_Mahalingam 30-Apr-15 14:04pm

yes,
initially i was wondered that there might be some other reason for this,but not -:) +5

Tomas Takac 30-Apr-15 14:43pm

I checked it just to be sure but there is really no difference. I know before (version 2000?) this kind of things mattered, but definitely not in version 2014. Old habits are just hard to change I guess. :)

Karthik_Mahalingam 30-Apr-15 14:47pm

:) of course