Debugging the Procedure Unable to Update Column in Oracle

As a technical blogger, I’ve encountered numerous issues while debugging procedures in Oracle. In this article, we’ll delve into the problem of updating a column in a table using an independent query in Oracle.

Understanding Independent Queries in Oracle

In Oracle, an independent query is a separate SQL statement that can be executed independently without affecting the execution of another query. Independent queries are useful when you need to perform calculations or aggregations on a large dataset without impacting the performance of your main application.

However, when working with independent queries, it’s essential to understand how they interact with each other, especially when updating data in a table.

The Problem: Updating Column Not Working

The problem at hand is an independent query that updates two variables (DSL_HOUR_DIVIDEND and ELEC_HOUR_DIVIDEND) and then uses these values to update another column in the GBL_TMP_SUMMARY_CNT table. However, the update operation fails, leaving the value of the updated column unchanged.

The Issue with the WHERE Clauses

The issue lies in the WHERE clauses used in the UPDATE statement. As highlighted in the Stack Overflow post, there’s a difference between the WHERE clause used in the SELECT statement and the UPDATE statement:

SELECT statement: SUB_ITEM_NO IN (5.04, 5.05)
UPDATE statement: WHERE A.ITEM_NO = 5 AND A.SUB_ITEM_NO = 5.06 AND A.SUB_SUB_ITEM_NO = 'B'

The difference in WHERE clauses is crucial to resolving the issue.

Debugging Steps

To resolve this problem, we need to follow these debugging steps:

Step 1: Verify the Values Being Assigned

First, verify that the values being assigned to the variables (DSL_HOUR_DIVIDEND and ELEC_HOUR_DIVIDEND) are correct. This can be done by adding print statements or using a debugger to inspect the values.

-- Assigning values to variables
SELECT DSL_HOUR_DIVIDEND, ELEC_HOUR_DIVIDEND INTO 
    :DSL_HOUR_DIVIDEND,
    :ELEC_HOUR_DIVIDEND 
FROM (SELECT ITEM_NO,
               SUB_ITEM_NO,
               SUB_SUB_ITEM_NO,
               SUM(SUB_SUB_ITEM_VALUE_DSL) AS SUB_SUB_ITEM_VALUE_DSL,
               SUM(SUB_SUB_ITEM_VALUE_ELEC) AS SUB_SUB_ITEM_VALUE_ELEC
          FROM REPORT.DY_SUM_DLY_DAILY
         WHERE REPORT_DATE > '01-Mar-2020'
           AND REPORT_DATE <='07-Mar-2020'
           AND SUB_ITEM_NO IN (5.04, 5.05)
         GROUP BY ITEM_NO,
                  SUB_ITEM_NO,
                  SUB_SUB_ITEM_NO);

Step 2: Verify the Row Being Updated

Next, verify that a row exists in the GBL_TMP_SUMMARY_CNT table that matches the conditions specified in the UPDATE statement.

-- Verifying the row being updated
SELECT *
FROM REPORT.GBL_TMP_SUMMARY_CNT A
WHERE A.ITEM_NO = 5
   AND A.SUB_ITEM_NO = 5.06
   AND A.SUB_SUB_ITEM_NO = 'B';

Step 3: Update and Verify Again

If a row exists in the table, update the value of the column as specified in the UPDATE statement and verify that it has been updated correctly.

-- Updating the column
UPDATE REPORT.GBL_TMP_SUMMARY_CNT A
SET CY_DSL_CNT = ROUND(DSL_HOUR_DIVIDEND / DSL_HOUR_DIVISOR * 100, 2),
    ELEC_HOUR_DIVIDEND = ELEC_HOUR_DIVIDEND
WHERE A.ITEM_NO = 5
   AND A.SUB_ITEM_NO = 5.06
   AND A.SUB_SUB_ITEM_NO = 'B';

Conclusion

In conclusion, the issue of updating a column in Oracle is often related to inconsistent WHERE clauses between SELECT and UPDATE statements. By following these debugging steps, you can identify and resolve issues with your queries and ensure that data is updated correctly.

Remember to verify the values being assigned, check for existing rows in the table, and update the column as specified in the UPDATE statement to avoid common pitfalls when working with independent queries in Oracle.

Example Use Cases

Here’s an example use case where we can apply these debugging steps:

-- Creating a procedure to update a column in the GBL_TMP_SUMMARY_CNT table
CREATE OR REPLACE PROCEDURE update_column(
    p_dsl_hour_dividend IN NUMBER,
    p_elec_hour_dividend IN NUMBER
) AS
BEGIN
    UPDATE REPORT.GBLTmpSummaryCnt A
    SET CY_DSL_CNT = ROUND(p_dsl_hour_dividend / p_dsl_hour_dividend * 100, 2),
        ELEC_HOUR_DIVIDEND = p_elec_hour_dividend
    WHERE A.ITEM_NO = 5
       AND A.SUB_ITEM_NO = 5.06
       AND A.SUB_SUB_ITEM_NO = 'B';
END;

In this example, we create a procedure update_column that takes two input parameters: p_dsl_hour_dividend and p_elec_hour_dividend. We then update the column in the GBL_TMP_SUMMARY_CNT table using these values.

Troubleshooting Tips

Here are some troubleshooting tips for common issues when working with independent queries in Oracle:

Inconsistent WHERE clauses: Double-check that the WHERE clause used in the SELECT statement is consistent with the UPDATE statement.
Missing rows: Verify that a row exists in the table that matches the conditions specified in the UPDATE statement.
Invalid data types: Ensure that the data type of the input parameters is correct and compatible with the column being updated.

By following these debugging steps, troubleshooting tips, and best practices for independent queries in Oracle, you can resolve issues and write efficient and effective code.

Last modified on 2025-03-11