Relational Databases 101—Unicode vs. ANSI

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Unicode vs. ANSI

In situations where you need to store data in an "international" character set, whose characters are not supported by the ANSI set, you'll have to define your columns (and string literals) as Unicode. If you take this option, SQL Server stores 16 bits for each character instead of 8. It means the same four-character entry requires 4 bytes in ANSI and 16bytes in Unicode columns. Just remember to prefix your string literals with N, as in N'Fred', when building Unicode expressions—Visual Studio tools and wizards do this for you if they generate the query. There is another aspect to Unicode that might surprise you. When you define a column as nvarchar, you specify a maximum length, as shown in Figure 3.8.

Figure 3.8 Creating a table with a Unicode column.

This DDL code allocates 50 bytes of space in the data row to the Author's name. However, this also means that the name must be no longer than 25 (16-bit) characters.