Using PatIndex and CharIndex like the InStr function

Question

I tried using Instr for this, but didn't work, so I found the supposed to be equivalent using PatIndex and CharIndex, however, I'm having an issue here when I run this:

SELECT PATINDEX(`http://www.stackoverflow.com`,'%.com%')

This returns 0

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SELECT CHARINDEX(`http://www.stackoverflow.com`,'%.com%')

This returns 0

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SELECT PATINDEX(`http://www.stackoverflow.com`,'.com')

This returns 0

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SELECT CHARINDEX(`http://www.stackoverflow.com`,'.com')

This returns 0

---

How do I get this to work like InStr ?

If my calculation is correct, it should return 25 instead of 0, anyone know why it's not?

Answer 1

You've got it reversed.

select patindex('%.com%', 'http://www.stackoverflow.com');
select charindex('.com', 'http://www.stackoverflow.com');

Answer 2

Be careful while using those functions in computed column functions. Because they are non-deterministic.

https://technet.microsoft.com/en-us/library/aa214775(v=sql.80).aspx