Should I use != or <> for not equal in T-SQL?

Most databases support != (popular programming languages) and <> (ANSI).

Databases that support both != and <>:

MySQL 5.1: != and <>

PostgreSQL 8.3: != and <>

SQLite: != and <>

Oracle 10g: != and <>

Microsoft SQL Server 2000/2005/2008/2012/2016: != and <>

IBM Informix Dynamic Server 10: != and <>

InterBase/Firebird: != and <>

Apache Derby 10.6: != and <>

Sybase Adaptive Server Enterprise 11.0: != and <>

Mimer SQL 11.0: != and <>

Databases that support the ANSI standard operator, exclusively:

IBM DB2 UDB 9.5: <>

Microsoft Access 2010: <>

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Technically they function the same if you’re using SQL Server AKA T-SQL. If you're using it in stored procedures there is no performance reason to use one over the other. It then comes down to personal preference. I prefer to use <> as it is ANSI compliant.

You can find links to the various ANSI standards at...

http://en.wikipedia.org/wiki/SQL

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'<>' is from the SQL-92 standard and '!=' is a proprietary T-SQL operator. It's available in other databases as well, but since it isn't standard you have to take it on a case-by-case basis.

In most cases, you'll know what database you're connecting to so this isn't really an issue. At worst you might have to do a search and replace in your SQL.

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The ANSI SQL Standard defines <> as the "not equal to" operator,

http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt (5.2 <token> and <separator>)

There is no != operator according to the ANSI/SQL 92 standard.

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<> is the valid SQL according to the SQL-92 standard.

http://msdn.microsoft.com/en-us/library/aa276846(SQL.80).aspx

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It seems that Microsoft themselves prefer <> to != as evidenced in their table constraints. I personally prefer using != because I clearly read that as "not equal", but if you enter [field1 != field2] and save it as a constrait, the next time you query it, it will show up as [field1 <> field2]. This says to me that the correct way to do it is <>.

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They're both valid and the same with respect to SQL Server,

https://docs.microsoft.com/en-us/sql/t-sql/language-elements/not-equal-to-transact-sql-exclamation

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!=, despite being non-ANSI, is more in the true spirit of SQL as a readable language. It screams not equal. <> says it's to me (less than, greater than) which is just weird. I know the intention is that it's either less than or greater than hence not equal, but that's a really complicated way of saying something really simple.

I've just had to take some long SQL queries and place them lovingly into an XML file for a whole bunch of stupid reasons I won't go into.

Suffice to say XML is not down with <> at all and I had to change them to != and check myself before I riggedy wrecked myself.

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You can use whichever you like in T-SQL. The documentation says they both function the same way. I prefer !=, because it reads "not equal" to my (C/C++/C# based) mind, but database gurus seem to prefer <>.

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I understand that the C syntax != is in SQL Server due to its Unix heritage (back in the Sybase SQL Server days, pre Microsoft SQL Server 6.5).

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One alternative would be to use the NULLIF operator other than <> or != which returns NULL if the two arguments are equal NULLIF in Microsoft Docs. So I believe WHERE clause can be modified for <> and != as follows:

NULLIF(arg1, arg2) IS NOT NULL

As I found that, using <> and != doesn't work for date in some cases. Hence using the above expression does the needful.

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I preferred using != instead of <> because sometimes I use the <s></s> syntax to write SQL commands. Using != is more handy to avoid syntax errors in this case.

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Both works and I think any difference would be very negligible! Just focus on productivity guys!

What is the value of your script? What does it do? How will it contribute to the business? Will it make more money?

Focus on these goals instead of these programmer prefered preferences. This is like which is better C# or Visual Basic languages. As if the end user cares what was used to write the App?

What the end user cares about is what your App could do. How could it help him with what he is doing.

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They are both accepted in T-SQL. However, it seems that using <> works a lot faster than !=. I just ran a complex query that was using !=, and it took about 16 seconds on average to run. I changed those to <> and the query now takes about 4 seconds on average to run. That's a huge improvement!

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