SQL Server 2016

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CREATE TABLE VarcharNonClustered
(
	ID INT
	,Name VARCHAR(2000)
)
CREATE NONCLUSTERED INDEX idx_VarcharNonClustered_Name ON VarcharNonClustered(Name)
Warning! The maximum key length for a nonclustered index is 1700 bytes. The index 'idx_VarcharNonClustered_Name' has maximum length of 2000 bytes. For some combination of large values, the insert/update operation will fail.


INSERT INTO VarcharNonClustered 
VALUES (1,REPLICATE('a',1701))
Msg 1946 Level 16 State 3 Line 1
Operation failed. The index entry of length 1701 bytes for the index 'idx_VarcharNonClustered_Name' exceeds the maximum length of 1700 bytes for nonclustered indexes.

INSERT INTO VarcharNonClustered 
VALUES (1,REPLICATE('a',1700))
1 rows affected

INSERT INTO VarcharNonClustered 
VALUES (1,REPLICATE('a',901))
1 rows affected

INSERT INTO VarcharNonClustered 
VALUES (1,REPLICATE('a',900))
1 rows affected