CAST vs. CONVERT in T-SQL: Which Data Conversion Function Should You Choose?

T-SQL data type conversion: choice between CAST and CONVERT

In T-SQL, both CAST and CONVERT are used to convert data from one type to another. However, there are subtle differences between the two that may affect your choice.

When to use CAST vs. CONVERT

• ANSI Standards Compliance: CAST conforms to the ANSI SQL standard, while CONVERT is specific to SQL Server. If portability is an issue, CAST is preferred.
• Flexibility: CONVERT provides greater flexibility in formatting dates and other data types. CONVERT provides greater control if you require a specific output format.

Performance Considerations

Generally, there is no significant performance difference between CAST and CONVERT. Implicit conversions (without using any function) may cause a loss of precision, but CAST and CONVERT explicitly control data conversion and prevent this problem.

Suggestion

Based on the above considerations, it is recommended to use CAST whenever possible. It follows ANSI standards, eliminates loss of precision, and provides a consistent method of data conversion. CONVERT should be used only when specific formatting requirements require its use.

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