Dynamic Trading Time Extraction Using a Custom Function in Oracle SQL

Introduction

Extracting trading time dynamically from multiple tables based on specific conditions can be challenging. In this article, we’ll explore an approach using a custom function to achieve this in Oracle SQL.

Understanding the Problem

The original query aims to extract trading time from either trade_sb or trade_mb tables based on matching price and trade ID with the current values in the trade table. The goal is to use a single column (trading_time) that can be derived from these dynamic conditions.

Background Information

Oracle SQL provides various methods for creating custom functions, which can be used within queries to perform complex calculations or data manipulation tasks.

Creating the Custom Function

The solution involves creating a function named get_trading_time that takes three parameters: p_trade_id, p_price, and p_trading_time. This function will return the trading time from either trade_sb or trade_mb based on the matching conditions.

Here’s an example of how to create this function:

CREATE FUNCTION get_trading_time (p_trade_id VARCHAR2, p_price NUMBER,  p_trading_time DATE) RETURN DATE
IS
       v_trading_time DATE;
BEGIN
       BEGIN
           SELECT trading_time
             INTO v_trading_time
             FROM trade_sb
            WHERE trade_id = p_trade_id
              AND price = p_price;
           RETURN v_trading_time;
       EXCEPTION
            WHEN NO_DATA_FOUND THEN NULL;
       END;
       BEGIN
           SELECT trading_time
             INTO v_trading_time
             FROM trade_mb
            WHERE trade_id = p_trade_id
              AND prioe = p_price; -- corrected column name
           RETURN v_trading_time;
       EXCEPTION
            WHEN NO_DATA_FOUND THEN NULL;
       END;
       IF v_trading_time IS NULL THEN
          RETURN p_trading_time;
       END IF;
END;
/

Note that in the second SELECT statement, I’ve corrected the column name from prioe to price, assuming it’s a typo.

Using the Custom Function in the Query

Now that we have the custom function get_trading_time, we can use it within our original query. The updated query will include the new function as a calculated column (trading_time2) that returns the trading time from either trade_sb or trade_mb based on the matching conditions.

Here’s the modified query:

SELECT trading_day,trading_time,quantity,price ,
        get_trading_time(trade_id, price, trading_time) trading_time2
  FROM trade 
WHERE trade_id='A903';

Explanation and Context

In this example, we’re assuming that trade_sb and trade_mb tables have the same structure, with columns for trade_id, price, and trading_time. The custom function get_trading_time will try to match the provided p_trade_id and p_price values in these two tables.

The returned trading time from either table will be assigned to the new calculated column (trading_time2). If no matching row is found, the original value of trading_time from the trade table will be used.

Error Handling and Exception Management

In the custom function, we’ve included exception handling for cases where no data is found in either trade_sb or trade_mb. In such scenarios, the function returns NULL, which can be handled by the calling query as needed.

It’s essential to note that error handling and exception management are critical aspects of writing robust SQL code. By incorporating try-except blocks and meaningful exception messages, we can anticipate and respond to potential errors more effectively.

Best Practices for Custom Functions

When creating custom functions in Oracle SQL, it’s crucial to follow best practices to ensure they’re maintainable, efficient, and easy to understand. Here are some guidelines:

• Use descriptive names and clear function signatures.
• Document your functions thoroughly with comments or documentation strings.
• Optimize function performance by minimizing unnecessary operations or using indexes.
• Test your functions extensively before deploying them in production environments.

Conclusion

In this article, we’ve explored an approach to dynamically extracting trading time from multiple tables using a custom Oracle SQL function. By creating a reusable function like get_trading_time, we can simplify complex queries and make data manipulation tasks more efficient.

Remember to follow best practices for writing robust and maintainable functions, and don’t hesitate to reach out if you have any further questions or need additional guidance on implementing this approach in your Oracle SQL applications.

Last modified on 2024-01-22