How to Retrieve Multiple ROWIDs from Tables in Oracle PL/SQL

Learn how to efficiently gather multiple ROWIDs from several tables in Oracle PL/SQL, storing them in collections for easy manipulation.
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Retrieving Multiple ROWIDs from Tables in Oracle PL/SQL

When working with databases, especially in Oracle PL/SQL, you might encounter scenarios where you need to retrieve specific identifiers, called ROWIDs, from multiple tables. One common problem is efficiently gathering these ROWIDs based on certain conditions, such as the presence of line breaks in specific columns. In this guide, we'll walk you through the process of looping through multiple tables and storing the retrieved ROWIDs in an array for further use.

The Challenge

Imagine you have a list of tables stored in a database, and within those tables, you want to find rows that contain line breaks. You also want to store all the ROWIDs of those matching rows. The typical approach would be to create a cursor to loop through these tables, but you may run into issues if your code is designed to handle only single values. So, how do you modify it to store multiple ROWIDs?

Understanding the Solution

To tackle this, you will need to utilize collections in PL/SQL, which allow you to hold multiple values. Below, we break down the complete solution step by step:

Step 1: Define a Collection

First, you need to declare a collection type that can hold ROWIDs. This collection will allow you to gather multiple ROWID values effectively.

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In this snippet:

We declare a collection type rowid_t which can store ROWIDs indexed by integers.

l_rowids is an instance of this collection type.

Step 2: Loop Through Tables

Next, you will loop through the list of tables and run a dynamic SQL statement to fetch the desired ROWIDs from each table.

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Here, we use a FOR loop to select the relevant metadata from your table.

The EXECUTE IMMEDIATE statement fetches the ROWIDs based on the line-break condition (INSTR() function checks for chr(10)).

We use BULK COLLECT INTO to gather all the results into l_rowids efficiently.

Step 3: Logging the Results

Once you have the collected ROWIDs, you can easily process or log them into another table.

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This loop iterates through the collected ROWIDs, inserting them into log_tabla along with the respective column and table names.

Complete Code

Bringing it all together, your complete PL/SQL block will look like this:

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Conclusion

By utilizing collections in PL/SQL, you can efficiently retrieve and manage multiple ROWIDs from a selection of tables. With the above example, you'll be able to tackle similar problems in your Oracle DB environment. Always remember to adapt your logic based on how many entries you expect - collections are a powerful way to handle batch data processing!

Now you're ready to enhance your database management skills and streamline your PL/SQL operations! Feel free to reach out with any questions or comments about this process.