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

Question

I have seen SQL that uses both != and <> for not equal. What is the preferred syntax and why?

Answer 1

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 <>

Databases that support the ANSI standard operator, exclusively:

• IBM DB2 UDB 9.5: <>
• Microsoft Access 2010: <>

Answer 2

!=, 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.

Answer 3

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!

Answer 4

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

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

Answer 5

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 <>.

Answer 6

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.