Скачать или смотреть How to Select Multiple Rows in Android SQLite Using rawQuery

Learn how to effectively select multiple rows in Android SQLite with `rawQuery`. Discover a clear solution for handling multiple values without breaking your ListView functionality.
---
This video is based on the question https://stackoverflow.com/q/62431071/ asked by the user 'CharlieH' ( https://stackoverflow.com/u/4374408/ ) and on the answer https://stackoverflow.com/a/62431931/ provided by the user 'forpas' ( https://stackoverflow.com/u/10498828/ ) 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: Android SQLite rawQuery - How to select multiple rows of a table

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.
---
Selecting Multiple Rows in Android SQLite with rawQuery

When working with databases in Android, you might run into a situation where you need to retrieve multiple rows from a table. This is a common requirement, and using SQLite's rawQuery can help you achieve it. However, many developers face challenges when attempting to pass multiple parameters to the rawQuery method, particularly when the result displays an empty ListView. In this post, we will break down how to effectively select multiple rows in Android SQLite using rawQuery.

The Problem

The Scenario

Imagine you have a table called recipes, and you want to fetch multiple rows based on their unique identifiers (_id). While querying with a single _id works perfectly fine, an attempt to use multiple IDs (for example, 2 OR 5) often leads to an empty result set. This could be frustrating, especially when you're trying to display these results in a ListView.

Example of the Issue

[[See Video to Reveal this Text or Code Snippet]]

The Solution

To solve this problem, there is a cleaner and more efficient way to pass multiple values in a single query. Rather than constructing complex SQL statements, we can utilize the LIKE operator in combination with a comma-separated value string.

Step-by-step Guide

Construct a Comma-Separated String:
Instead of entering multiple IDs as separate array elements, you can create a single string that joins all the IDs with commas. For instance, if you want to select recipes with IDs 1, 2, and 3:

[[See Video to Reveal this Text or Code Snippet]]

Modify the SQL Query:
You can then adjust your SQL query to use the LIKE operator. Here’s how you can do it:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Query:

The SQL syntax ',' || ? || ',' ensures that the IDs are surrounded by commas. This method allows the query to check if each _id exists within the provided string.

The LIKE condition checks if an _id matches any of the IDs in the string, allowing for a successful retrieval whether you're querying for a single or multiple IDs.

Advantages of This Approach

Simplicity: This method eliminates the need to write cumbersome SQL statements with multiple placeholders (e.g., ?).

Flexibility: It works seamlessly whether you are querying for one ID or multiple IDs.

Maintainability: Keeping your queries simple and cleaner makes your codebase easier to read and maintain.

Conclusion

With this approach, you can efficiently select multiple rows from a table in Android SQLite using rawQuery. By utilizing a single comma-separated string and leveraging the LIKE operator, you can handle multiple values easily without the dread of empty result sets. Always remember that how you construct your queries matters, and finding simple solutions can save you a lot of headaches down the line!

Try implementing this solution in your own applications, and you'll find that fetching multiple rows becomes a breeze!