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When I run the following query in SQL Server 2019, the result is 1, whereas it should be 0.

select CHARINDEX('αρ', 'αυρ')

What could be the problem?

marc_s
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orman
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    The fact that you didn't put `N` in front of your literals to specify `N[VAR]CHAR`, and hence are at the mercy of whatever your default `[VAR]CHAR` collation supports. If you do `SELECT 'αρ', 'αυρ', N'αρ', N'αυρ'`, you should see how your strings get mangled. – Jeroen Mostert Oct 30 '20 at 19:08
  • If I define any field in the table as nvarchar (max),is it automatically gets N ? Because I wrote an sql function and when i run it select DBO.splitstring( N'αυρ',N'αρ') /* resul is 0 */ , but when i run this , select * from [yazitlar] where dbo.splitstring([yazit], N'αρ' ) = 1 order by idx /* [yazit] is nvarchar(max) and the returning row just contain Αὐρ */ – orman Oct 30 '20 at 19:34
  • Does this answer your question? [What is the meaning of the prefix N in T-SQL statements and when should I use it?](https://stackoverflow.com/q/10025032/2029983) – Thom A Oct 30 '20 at 19:37
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    This may well have to do with how your `dbo.SplitString` function is defined, which is not in the question. And note that `Αὐρ` is not `αυρ` -- whether these strings are considered identical or not, even when they're not mangled, depends on the collation of the column (which is typically the collation of your database, but can be different). The collation dictates comparison results, which apply to `VARCHAR` and `NVARCHAR` alike; for `VARCHAR` it also determines what characters can be stored. – Jeroen Mostert Oct 30 '20 at 19:45
  • Ok thank you Jeroen , i suppose i am missing something. – orman Oct 30 '20 at 19:50
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    I was able to identify the problem more clearly ; select CHARINDEX( N'αρ',N'αὐρ' ) result is 1 , select CHARINDEX( N'αρ', N'αυρ') result is 0 – orman Oct 30 '20 at 20:08

1 Answers1

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As was mentioned in the comments it may be because you have not declared your string literals as Unicode strings but are using Unicode characters in the strings. SQL Server will be converting the strings to another codepage and doing a bad job of it. Try running this query to see the difference.

SELECT 'αρ', 'αυρ', N'αρ', N'αυρ'

On my server, this gives the following output:

a? a?? αρ αυρ

Another issue is that CHARINDEDX uses the collation of the input which I think is probably not set correctly in this instance. You can force a collation by setting it on one of the inputs. It is also possible to set it at the instance, database and column level.

There are different collations that may be applicable. These have different features, for example some are case sensitive some are not. Also not all collations are installed with every SQL Server instance. It would be worth running SELECT * from sys.fn_helpcollations() to see the descriptions of all the installed ones.

If you change your query to this you should get the result you are looking for.

SELECT CHARINDEX(N'αρ' COLLATE Greek_BIN, N'αυρ')
Martin Brown
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  • actually making unicode doesn't change the situation, select CHARINDEX( N'αρ',N'αὐρ' ) result = 1 , and select CHARINDEX( N'αρ', N'αυρ') result = 0 Greek spiritus lenis ignores the character which it came upon – orman Oct 30 '20 at 21:08
  • I've added some extra text to my answer regarding collations. – Martin Brown Nov 01 '20 at 12:19
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    Thank you so much Martin, the problem was fixed when I chose collate as Greek_BIN. – orman Nov 01 '20 at 20:21