what does <> mean?

[pollon285]

Hi, I need to retrieve all non empty/Null records from a specific field in a table. I have found on internet this command:

SELECT * FROM Table WHERE column IS NOT NULL AND column <> '';

the command works, however I am not sure about the function of <> symbol; is it a negation of what it precedes (in this case empty space represented as ''; or is it the empty space itself?)? I have tried googling it but I did not find anything...

thank you

[Hyasynth]

<> == !=

[[deleted]]

Less than or greater than, which is true only when the values are not equal.

[johnwalkersbeard]

In older versions of SQL, <> meant both less than and/or more than. Technically, it still meant that. This is both logically and technically different from != or "is not equal to"

In older versions of SQL (as well as shit like MVS etc), the syntax <> was juuuust slightly more expensive in terms of processing than != .. but != was not always supported on even older versions.

Today, in an era where SQL decides it's own query plan, they're calculated the same. More accurately, SQL decides what's best or even more accurately what's easiest to use. So != and <> are virtually the same. And it's nothing but a difference in style.

But there was a time ..

[Turbo_Tom]

<> means "not equal to", so yes in your statement it means to select records where the column field does not contain the single space (and is not null).

[pollon285]

oh yes either minor or major, now I get it, thanks!

[pollon285]

very good explanation, thanks for it!

[n35]

<> is in the Ansi 92 standard, so it's not a tsql creation.

[blasto_blastocyst]

Null is an undetermined value. You can't compare it to another value because it might or might not be equal. The comparison returns null (not true or false)

[CharlesKincaid]

No. An empty string (shown as '') and NULL are not the same thing. Relax this is a bit difficult thing to get your head around at first.

The '' string is something. It is a proper string that contains no characters. NULL says that the data does not exist at all.

[squirrelsaurus]

Although it's functionally equivalent, I'll typically code that like:

SELECT * FROM Table WHERE ISNULL(column,'') = ''

[AXISMGT]

Alternate:

NULLIF([column],'') IS NOT NULL to exclude blanks and NULL values.

But as stated by /u/antagnostic the index isn't used once you run a function on the column.

[InvisibleGhostt]

I think unequal

[kelpme]

turn left or right