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How to Retrieve Historical Data from a Temporal Table?


Retrieving Historical Data from a Temporal Table

Write a SQL query to retrieve historical data from a temporal table.

Solution:

-- Retrieve historical data from the EmployeeHistory table.
SELECT EmployeeID, Name, Position, SysStartTime, SysEndTime
FROM EmployeeHistory;

Explanation:

  • Purpose of the Query :
    • The goal is to demonstrate how to query historical data stored in the history table.
  • Key Components :
    • EmployeeHistory: Refers to the history table containing past versions of rows.
    • Includes SysStartTime and SysEndTime to track when each version was valid.
  • Why Query Current Data:
    • Historical data provides insights into changes over time, supporting auditing and trend analysis.
    • It helps reconstruct past states of the database.
  • Real-World Application :
    • In financial systems, historical data tracks account balance changes.

Additional Notes:

  • Use the history table for compliance, debugging, or point-in-time analysis.
  • Combine historical data with current data for comprehensive reporting.
  • Important Considerations:
    • Regularly archive old records to manage storage growth.

For more Practice: Solve these Related Problems:

  • Write a SQL query to retrieve all historical versions of a specific product from a temporal Products table.
  • Write a SQL query to fetch historical employee records from an EmployeeHistory table where the position was changed.
  • Write a SQL query to display all past states of a customer's address from a temporal Customers table.
  • Write a SQL query to analyze historical sales data from a temporal Sales table to identify trends over time.

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