Скачать или смотреть How to Compare Dates Across Tables in Oracle SQL

Learn how to effectively compare dates between two tables in Oracle SQL and identify mismatches in your data relationships.
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Understanding the Problem: Date Comparisons in Oracle SQL

When working with databases, ensuring the accuracy of your data is crucial. One common issue arises when dates are compared across multiple tables, leading to potential mismatches in relationships. A user faced this problem with two tables: START_PERIOD and APPLICATION_FORM. In this guide, we'll explore how to identify and correct these mismatches using Oracle SQL.

The Table Structures

The first step to understanding the problem involves looking at the two tables involved:

START_PERIOD Table

This table holds the duration of time periods with the following structure:

id: Unique identifier for each period.

start_date: Beginning date of the period.

end_date: Ending date of the period.

Here's a sample from the START_PERIOD table:

idstart_dateend_date101/01/202231/03/2022201/04/202230/06/2022301/07/202230/09/2022401/10/202231/12/2022APPLICATION_FORM Table

This table captures user applications, containing the following fields:

CS_START_DATE: A date field representing when the application starts.

SP_ID: The identifier referencing the START_PERIOD table.

For example, if CS_START_DATE is 01/02/2022, the corresponding SP_ID should match the id of START_PERIOD where CS_START_DATE falls between START_DATE and END_DATE.

Identifying the Issues

The main issue arises when the SP_ID does not accurately reflect the correct date range for CS_START_DATE. The objective is to ensure SP_ID correctly matches the corresponding entry from START_PERIOD based on CS_START_DATE.

The SQL Solution

To tackle this, we can write a SQL query that identifies the correct id from START_PERIOD based on CS_START_DATE in APPLICATION_FORM. Here's how to do it:

SQL Query

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Query

SELECT Statement: We are retrieving both the correct id from the START_PERIOD table and the incorrect_id from APPLICATION_FORM.

FROM Clause: We are querying from both tables (start_period and application_form).

WHERE Clause: This is the crucial part. We use the BETWEEN operator to check if the CS_START_DATE falls within the range defined by start_date and end_date.

Conclusion

By executing this query, you'll be able to retrieve both the correct id and the currently assigned SP_ID for each application, allowing you to identify any mismatches. Ensuring that your IDs align with the date ranges provided in START_PERIOD not only helps maintain data integrity but also improves the accuracy of your reports and analysis.

If you need further assistance with complex queries or data integrity issues, consider reaching out to a database professional or exploring more Oracle SQL resources. Happy querying!