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Learn how to store the results of a `GROUP BY` clause into a variable in Oracle PL/SQL with clear examples.
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Storing GROUP BY Results in Oracle PL/SQL Variables

When working with databases, handling grouped data can often present challenges, especially when we want to store these results within a variable for later use. This guide will address how to store the output of a GROUP BY clause in a variable using Oracle PL/SQL, a powerful procedural extension for SQL.

Understanding the Problem

Many developers have encountered the need to run a GROUP BY SQL query where the output needs to be collected and stored into a PL/SQL variable. In our example, let's say we want to count members in different organizations and store those results for future processing.

Here’s a sample SQL query that you might use:

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However, to capture the results from this query in a PL/SQL variable, we need to define an appropriate variable type and structure to hold our results. In the next sections, we will walk through how to achieve this with examples.

Steps to Store GROUP BY Results

1. Define Object Types for Your Data

The first step is to declare types that will represent the structure of the data you’re collecting. You need to provide a way to hold both the ORG_NAME and their respective counts. Below are two methods to do this:

Method 1: Using PL/SQL Record Types

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In this method, we’re defining a record type ttar to hold each row, and then a VARRAY type ttav to store multiple records.

Method 2: Using SQL-Level Object Types

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This approach registers the types at the database level, which can be beneficial for modularity and ease of reuse in other PL/SQL blocks.

2. Collecting the Results

Once the types are defined, we can perform the query and collect the results into our defined variable.

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Use the BULK COLLECT INTO clause to gather the results of the grouped query directly into the defined variable ttab.

3. Processing the Results

After collecting the data, you can loop through your variable and process the information as needed.

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In this loop, we output each organization and its respective count.

Example Output

For an example with the data in the dept and emp tables, the output might look like this:

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Conclusion

Storing results from a GROUP BY clause in PL/SQL allows for flexible manipulation and processing of aggregated data. Whether you choose to declare types in PL/SQL or at the SQL level, the method outlined above can help you store and work with grouped data effectively.

By following the structure laid out in this guide, you'll be equipped to handle these types of database queries seamlessly, improving both performance and maintainability in your Oracle applications.