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1DECLARE @S1 NVARCHAR(10) = '2';
2DECLARE @S2 NVARCHAR(10) = '²';
3DROP TABLE IF EXISTS #Test;
4CREATE TABLE #Test(S NVARCHAR(10) NOT NULL);
5CREATE UNIQUE INDEX I1 ON #Test(S);
6INSERT #Test SELECT @S1;
7INSERT #Test SELECT @S2;
8
9Msg 2601, Level 14, State 1, Line 7
10Cannot insert duplicate key row in object 'dbo.#Test' with unique index 'I1'. The duplicate key value is (²).
11The statement has been terminated. 
12     
13var b = SqlString.Equals("2", "²");