Should I use != or <> for not equal in T-SQL?
In T-SQL, both !=and <> function as inequality operators. However, <> is preferred for its ISO standard adherence and wider compatibility.
An example in practice:
Choosing Not-Equal Operators: A Deep Dive
When deciding between !=and <>, there are a few considerations to keep in mind:
Uniformity within your codebase
Maintaining consistency across your project enhances readability. While != might feel more intuitive due to its usage in other languages, using <> aligns with SQL standards and is likely more familiar to anyone with a background in SQL.
Compatibility across different databases
In terms of compatibility, <> clearly takes the lead:
- SQL Server (2000-2016): Both
!=and<>are supported. - MySQL, PostgreSQL, Oracle: Both are valid, but
<>is standard-compliant. - IBM DB2 UDB 9.5 + Microsoft Access 2010: Only
<>is recognized.
Your exposure to different languages
If you're a Visual Basic programmer, <> might be your go-to option, purely out of habit. But remember, we're using SQL here, not VB. Think global, code local!
Don't underestimate official resources
Coding best practices can be subjective โ what's considered "correct" often depends on the context. Don't hesitate to consult official documentation and trusted community resources like the ANSI SQL standards on Wikipedia, to make an informed choice.
Migration Considerations
During database migrations or cross-database operations, using non-standard operators like != can lead to unexpected hitches. The good news? You can easily avoid these nightmares by sticking with the universally accepted <>.
Migrating with grace
Here's why using <> makes migrations smoother:
- Prevents possible errors during transitions.
- Universal compatibility: Good for independence and code sharing.
- Guarantee SQL standard compliance.
And if you ever find yourself needing to switch from != to <> or vice versa, most IDEs make it as easy as a few search and replace operations.
Performance: Are they really equal?
Believe it or not, when it comes to execution speed in T-SQL, != and <> are equally fast. The SQL Server treats both operators identically, so perceptions of one being faster than the other are simply an illusion.
Efficiency in performance
- The query execution times are identical, regardless of the operator used.
- When deciding on an operator, focus on readability and maintainability, rather than performance.
The Takeaway: Best Practices
Drawn from our discussion, here are some best practices:
- Stick to one operator within a project for code uniformity.
- Always choose
<>for ISO standard compliance and cross-database compatibility. - Agree on an operator as a team to avoid confusion.
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