T-SQL Not Equal Comparisons: Should I Use != or <>?

Optimization of inequality comparison in T-SQL: != and <>

When doing value comparisons in T-SQL, developers often face the question of which operator to choose: != or <>? This choice may affect consistency and performance.

Operator comparison

Most databases, including T-SQL, support the use of != (commonly used in programming languages) and <> (conforming to the ANSI SQL standard). However, in some cases, only ANSI standard operators are supported.

Preferred syntax

Although you may prefer != because of its greater familiarity with Visual Basic syntax, it is recommended to use the ANSI standard operators for the following reasons:

• Universal compatibility: ANSI-compliant databases, such as IBM DB2 UDB and Microsoft Access, only support <>. Using != in these environments will result in an error.
• Consistency: Adherence to ANSI standards improves code consistency across multiple databases.
• Readability: The <> operator is the internationally recognized "not equal" symbol, which enhances the readability of the code.

Performance impact

Using the correct operators may have a performance impact. While some developers report that != may be slightly faster in some cases, these performance differences are usually negligible. Therefore, operator selection should prioritize consistency and readability over performance optimization.

Conclusion

When comparing values ​​in T-SQL, the preferred operator is <> because of its universal compatibility, consistency, and readability. Although != may provide a slight performance advantage in some cases, it is not a significant factor in most applications. Adherence to ANSI standard operators ensures code compatibility, maintainability, and clarity across various databases.

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