Code Examples (SQL Server 2005)

Code Examples (SQL Server 2005)

Table Creation with Different Data Types:

This code creates two tables, one with nvarchar(50) and another with nvarchar(MAX):

CREATE TABLE MyTable1 (
  ID int PRIMARY KEY,
  Description nvarchar(50) NOT NULL
);

CREATE TABLE MyTable2 (
  ID int PRIMARY KEY,
  LongDescription nvarchar(MAX)
);

Potential Storage Overhead:

Imagine you typically store short descriptions (less than 50 characters) in MyTable1. Here's how nvarchar(MAX) might waste space:

• nvarchar(MAX) allocates 24 bytes of overhead even for small data.
• nvarchar(50) only allocates space for the actual characters (assuming less than 50).

Performance Impact (Hypothetical Query):

This is a hypothetical query to show potential performance difference:

SELECT * FROM MyTable1 WHERE Description LIKE '%search term%';

-- Compared to:

SELECT * FROM MyTable2 WHERE LongDescription LIKE '%search term%';

The query on MyTable1 (with smaller data type) might be faster for filtering based on description because it has less data to scan through.

1. Fixed-length nvarchar(n):

   • This is the most efficient choice if you know the maximum expected length of your text data.
   • Choose an appropriate value for n (number of characters) that accommodates most entries without wasting space.
   • Example: CREATE TABLE MyTable (ID int, TextData nvarchar(200)) (assuming text is usually under 200 characters).

2. Multiple nvarchar columns:

   • For highly variable text lengths with some predictable patterns, consider using multiple nvarchar columns with different sizes.
   • Example: Create separate columns for "Title" (shorter) and "Content" (longer).

3. XML or JSON:

   • If your text data has a structured format, consider storing it as XML or JSON.
   • This allows storing complex data within a single column while enabling querying specific elements.
   • Note: While SQL Server 2005 supports basic XML functionality, advanced features and JSON support came in later versions.

4. Separate Table for Large Text:

   • For truly massive and unpredictable text data, create a separate table with a single nvarchar(MAX) column.
   • Link this table to your main table using a foreign key relationship based on a common ID.
   • This keeps the main table size manageable and allows efficient querying of core data.