VARCHAR stores variable-length, non-Unicode character data in SQL Server, using an 8-bit code page unless a UTF-8 collation is applied. section 3.2
Mistake #7: assuming VARCHAR is always the most space-efficient string type. A VARCHAR(10) and CHAR(10) can both hold ten-character values, but fixed-length strings pad unused characters with spaces, while rows also carry storage metadata. section 3.2
US address columns
An address table might define CityName as VARCHAR(17), because Mooselookmeguntic and Kleinfeltersville have 17-character names, StateName as VARCHAR(48), and ZIP code as VARCHAR(10). For a consistently ten-character value, compare VARCHAR(10) with CHAR(10) instead of assuming the two choices consume identical storage. section 3.2
Listing 3.5 Updating the DepartmentCode column to a fixed-length string
ALTER TABLE dbo.Employees ALTER COLUMN DepartmentCode NCHAR(2) ;
Compare a fixed-length NCHAR column definition with VARCHAR when reviewing schema choices. section 3.2
