Performance considerations

The NCHAR data type is like the CHAR data type, and NVARCHAR is like the VARCHAR data type.

Localized collation depends on the sorting rules that the locale defines, not on the computer representation of the character (the code points). This difference means that the database server might perform complex processing to compare and collate NCHAR and NVARCHAR data. Therefore, access to NCHAR data might be slower with respect to comparison and collation than to access CHAR data. Similarly, access to data in an NVARCHAR column might be slower with respect to comparison and collation than access to the same data in a VARCHAR column.

Assess whether your character data must take advantage of localized order for collation and comparison. If code-set order is adequate, use the CHAR, LVARCHAR, and VARCHAR data types.