Ever found yourself needing a temporary holding space for data within your OpenEdge applications? That's precisely where temporary tables, or 'temp-tables' as they're commonly known, come into play. Think of them as scratchpads for your code – useful for holding intermediate results, passing data between different parts of your application, or even for quick sorting and filtering before you commit to permanent storage.
At its heart, defining a temp-table in OpenEdge is about telling the system what kind of data it will hold. You're essentially creating a structure, much like a regular database table, but it lives only for the duration of your session or a specific procedure. The syntax is quite straightforward. You'll use the DEFINE TEMP-TABLE statement, followed by a name for your temp-table, and then you list out the fields it will contain, specifying their data types and any formatting. For instance, you might define a temp-table to hold customer names and IDs:
DEFINE TEMP-TABLE CustomerTemp NO-UNDO
FIELD CustNum AS INTEGER
FIELD CustName AS CHARACTER FORMAT "x(50)"
.
This sets up a temporary structure named CustomerTemp with two fields: CustNum for an integer and CustName for a character string up to 50 characters long. The NO-UNDO clause is a common practice, indicating that changes to this temp-table won't be automatically rolled back if an error occurs, which is often desirable for temporary data.
One of the most common uses for temp-tables is passing data between different procedures or windows. Imagine you have a window that needs to display results from a background process. You can define a temp-table in the calling window, pass it as an OUTPUT parameter to the procedure, let the procedure populate it, and then the calling window can access the filled temp-table. Reference Material 1 gives a great example of this, showing how a .w (window) file defines a Return_Results temp-table and passes it to a .p (procedure) file for processing.
This ability to act as a data conduit is incredibly powerful. It allows for modular programming, where different parts of your application can work together without needing to directly manipulate each other's permanent data structures. The procedure can focus on its task, and the temp-table serves as a clean, well-defined way to hand back the outcome.
Beyond just passing data, temp-tables are also fantastic for performance. If you're dealing with large datasets and need to perform operations like sorting or finding unique records, a temp-table can often be much faster than querying the database repeatedly. Reference Material 3 touches on this, mentioning how JetOpenTemporaryTable functions (though this is more C++ focused) are designed for rapid storage and retrieval, and can be used for very fast sorting and de-duplication of record sets.
When you're working with temp-tables, especially in scenarios involving web applications or more complex data structures, you might encounter them being populated from various sources, like JSON data. Reference Material 2 hints at this, showing a scenario where array data is read back into a temp-table from a URL. This flexibility means temp-tables aren't just for internal application logic; they can bridge the gap between external data formats and your OpenEdge environment.
So, in essence, OpenEdge temp-tables are your versatile, in-memory workhorses. They provide a structured, efficient way to manage temporary data, facilitating communication between application components and boosting performance for data manipulation tasks. Understanding how to define and use them effectively is a key skill for any OpenEdge developer looking to build robust and responsive applications.
