What is the Purpose of the Undocumented SQL Server System Table `master..spt_values`?

Exploring the Mysterious master..spt_values System Table

The undocumented SQL Server system table master..spt_values has long captivated database professionals due to its cryptic nature and absence from official Microsoft documentation. Its origins lie in the Sybase database system, where scant documentation hinted at its role in translating internal system codes into user-friendly representations.

Deciphering its Structure

spt_values contains a predefined set of numerical ranges (0-2047), each corresponding to various internal system values. The table's columns—type, low, and high—are key to understanding its function:

• type: Indicates the category of the represented system value.
• low: The minimum value within a specific type range.
• high: The maximum value within a specific type range.

Unofficial Applications

Although not officially supported, master..spt_values appears in various community-created scripts and code examples for non-standard tasks:

• Partitioning columns using defined ranges.
• Generating numerical sequences within specified boundaries.
• Assisting in index creation.
• Constructing virtual calendars.
• Indirectly retrieving object descriptions.

Important Considerations

While some developers find master..spt_values useful for certain tasks, its undocumented status means its behavior is not guaranteed across SQL Server versions. Its structure or contents could change without notice, making its use in production environments highly risky.

In summary, master..spt_values remains a fascinating, albeit unsupported, element of SQL Server. Its practical applications are limited, yet its existence continues to pique the interest of database enthusiasts.

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