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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Previous SQL Exercise: Querying Current Data from a Temporal Table.
Next SQL Exercise: Retrieving Data as of a Specific Point in Time.