What is master..spt_values and How Can It Be Used in SQL Server?

Unveiling the Secrets of master..spt_values in SQL Server

The system table master..spt_values is a largely undocumented yet intriguing component of SQL Server, carrying a legacy from its Sybase origins. While Microsoft offers no official documentation, its purpose and functionality have been deduced through observation and analysis of system stored procedures.

The Role of master..spt_values

Essentially, master..spt_values acts as a lookup table, bridging the gap between internal system codes and their human-readable equivalents. It translates cryptic numerical values into user-friendly text representations within SQL Server.

Understanding the Table Structure

The table comprises three columns: type, low, and high. The type column specifies the category of values, while low and high define the value range for that category. Each row represents a specific value mapping. For example:

<code>type    low    high
------  -----  -----
FILE    1       1
FILE    2       2
FILE    3       3</code>

Here, the values 1, 2, and 3 within the FILE type are mapped to "primary file," "system file," and "user file" respectively (though the exact string values are implementation dependent).

Practical Applications and Important Considerations

While some developers have creatively utilized master..spt_values for tasks like column splitting, generating sequential numbers, and constructing virtual calendars, its undocumented status necessitates caution. The table's structure and contents are subject to change across SQL Server versions, potentially leading to code breakage. Therefore, it's strongly discouraged for production environments.

Despite its lack of official support, master..spt_values remains a fascinating historical remnant, offering a peek into the internal mechanisms of SQL Server.

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