Differences between CAST and CONVERT in T-SQL

Data and Databases
1

Hey everyone,

I’ve been working with T-SQL for a while now, and I’m a bit confused about when to use CAST and when to use CONVERT. Are there any real differences between them? I’m wondering if one is faster than the other or if there are specific situations where one is better.

Also, I’m curious if either of these functions is more standard in SQL. Does anyone know if one of them is closer to ANSI-SQL?

I’d really appreciate any insights or experiences you could share. Thanks in advance!

-- Example using CAST
SELECT CAST(123.45 AS INT) AS CastExample;

-- Example using CONVERT
SELECT CONVERT(VARCHAR(10), GETDATE(), 101) AS ConvertExample;

These are just simple examples. I’d love to hear about more complex cases where you’ve found one to be better than the other.

2

In my experience, CAST and CONVERT are quite similar in functionality, but CONVERT offers more flexibility, especially when dealing with date formats. I’ve found CAST to be more portable across different SQL implementations, aligning closer to ANSI-SQL standards. Performance-wise, I haven’t noticed significant differences in most scenarios.

However, CONVERT shines when you need specific date format conversions or when working with legacy systems that require particular data representations. For general type conversions, I tend to use CAST for its simplicity and readability.

One crucial point to consider is that neither function inherently outperforms the other in terms of execution speed. The choice often comes down to specific requirements of your project and personal coding preferences. When in doubt, I recommend using CAST for its broader compatibility unless you need CONVERT’s extended functionalities.

3

yo, CAST n CONVERT r pretty similar, but CONVERT’s got more tricks up its sleeve. i usually go with CAST cuz its simpler n works across different SQL flavors. but if u need fancy date stuff, CONVERT’s ur bud. speed-wise, they’re both chill. just pick wat fits ur style n project needs, u kno?

4

hey sophia! ever thought about how CAST and CONVERT might affect query plans? i’ve been wondering if one might be more optimized in certain scenarios. have u tried benchmarking them in your projects? what kinda complex data transformations are u dealing with? maybe we could brainstorm some cool use cases together!