How to Use Multiple ADOQuery for Filtering Data in Delphi скачать в хорошем качестве

How to Use Multiple ADOQuery for Filtering Data in Delphi

Learn how to efficiently manage multiple ADOQueries in Delphi for displaying filtered data on separate DBGrids without creating multiple queries. --- This video is based on the question https://stackoverflow.com/q/63074372/ asked by the user 'Pan Javlík' ( https://stackoverflow.com/u/10851658/ ) and on the answer https://stackoverflow.com/a/63078271/ provided by the user 'MartynA' ( https://stackoverflow.com/u/2663863/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Delphi - Multiple ADOQuery Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Handling Multiple ADOQuery in Delphi for Efficient Data Filtering If you're new to Delphi and looking to optimize your database interactions, you might encounter a common challenge when trying to display filtered data across multiple DBGrids using ADOQuery. This post walks you through a simple and effective solution that allows you to filter data dynamically without having to write multiple "WHERE" queries. Let's dive into the solution! The Challenge: Displaying Filtered Data You may find yourself needing to display certain entries from a database in multiple DBGrids—each showing a different subset of data. Traditionally, the approach would be to create various queries for each grid, but this can be cumbersome and inefficient, especially if you're dealing with a large amount of data. Your task is to create three separate DBGrids that share a connection to the same ADOQuery but display different filtered results. The main point you need to keep in mind is that you want to avoid using multiple "WHERE" clauses. The Solution: Utilizing TAdoDataSet The solution to this problem is relatively straightforward. Instead of creating separate queries, you can use the TAdoDataSet to clone your original ADOQuery and apply filters to each dataset. Here’s a simple example to illustrate how this can be done: Step-by-Step Code Implementation Clone the ADOQuery: For each grid you want to filter, you'll clone the original ADOQuery. Set the Filter for Each Clone: Use the Filter property of the TAdoDataSet to specify what data should be displayed. Enable the Filter: Make sure to set Filtered to True to apply the filter to your dataset. Here’s an example of how to do this in code: [[See Video to Reveal this Text or Code Snippet]] Key Points to Remember Automatic Updates: One of the benefits of using TAdoDataSet is that changes made in the filtered grids are automatically reflected back to the original ADOQuery and ultimately to the database. Live Binding Caution: If you're using Live Bindings, you might encounter issues with filtering. It’s recommended to close and reopen your datasets when making changes to filters to avoid unexpected behavior. Advanced Approach: Using FireDAC If you're working with Delphi Seattle or later, you could opt for using FireDAC instead of ADO. This implementation is slightly more complex but provides enhanced features. Here’s how you could set it up: FireDAC Code Implementation Setup Connection and Update Options: Set cached updates and auto-commit options in the FormCreate. [[See Video to Reveal this Text or Code Snippet]] Filtering Data for DBGrids: You can clone the cursor and apply filters as shown below: [[See Video to Reveal this Text or Code Snippet]] Important Considerations Ensure CachedUpdates is set to True for the FDQuery to maintain data integrity. Use ApplyUpdates to save any changes when closing the form to prevent data loss or discard. Conclusion Managing multiple ADOQueries in Delphi can be easily streamlined by utilizing TAdoDataSet or FireDAC for your filtering needs. This method minimizes the need for multiple queries while allowing you to efficiently display the required subsets of data across multiple DBGrids. With the techniques outlined in this post, you should have a clearer understanding of how to handle data filtering in Delphi, making your applications more efficient and easier to manage. Happy coding and have a perfect day!