Can Indexes Be Created on SQL Server 2000 Table Variables?

SQL Server 2000: Indexing Table Variables

Question: Is index creation possible on SQL Server 2000 table variables?

The answer is nuanced. In SQL Server 2000, indexes on table variables are implicitly created, meaning you can't explicitly define them. Instead, you achieve indexing through unique or primary key constraints.

Implicit Indexing Advantages:

• UNIQUE and PRIMARY KEY Constraints: These constraints automatically generate indexes.
• Clustered vs. Non-Clustered: Primary key indexes are clustered, while unique constraint indexes are non-clustered.
• Duplicate Prevention: Both types prevent duplicate key values.

Important Considerations:

• Non-Unique Clustered Indexes: These are not supported on table variables.
• Heap Tables: Indexes on heap tables are always non-clustered.

Illustrative Syntax:

<code class="language-sql">DECLARE @TEMPTABLE TABLE (
  [ID] [INT] NOT NULL PRIMARY KEY,
  [Name] [NVARCHAR] (255) COLLATE DATABASE_DEFAULT NULL,
  UNIQUE NONCLUSTERED ([Name], [ID])
);</code>

This example demonstrates creating a table variable with a primary key index on the ID column and a unique, non-clustered index on the Name column. Note that this is achieved through constraint definitions, not explicit CREATE INDEX statements.

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