Make sure that the RowSet instance is in scope as long as you need to access the records it contains. Take care of this when you start to work with RowSet instances: the row will be unlocked when we use the methods MoveToNextRow, to advance to the next record, MoveToPreviousRow to go back to the previous record, or if we close the RowSet executing the Close method or because the RowSet has become out of scope. The available class methods also allows us to know the total amount of records in the set using the RowCount method, delete the current record with the RemoveRow method or updating any of the record columns using the SaveRow method, always we have invoked the EditRow method previously, in first place, to instruct the DatabaseRow instance to block the record while we are modifying it, so it can't be modified also by other users. RowSet provides the methods we need to move from one record to another in the row set: moving to the next, returning to the previous one, setting the record pointer cursor again to the first record of the group or jumping to the last one. As you probably remember, that's the one we have been working with briefly in the previous SQLite Basics course. For that kind of operation, we use the RowSet class to work with the retrieved records from a SQL query. We can get just one record or a group of records. Sooner or later we will need to retrieve a set of rows (records) matching a specified criteria. So, for example, the previous snippet would be like this:
When using this syntax, we provide the '?' character as a placeholder of the value to be inserted in the SQL statement itself, followed by the real values in the expected order. In order to prevent these scenarios we can use other syntax for the ExecuteSQL method, known as a Prepared Statement. But, what happened if the data to insert in a new record comes from the user? In that cases we can be faced to scenarios where the user introduces some specific characters as part of the input itself that can result in what is know as SQL injection attacks.
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That is not a bad thing if the data is generated in code (because you're probably in control about what is going to be inserted). If we forget any of these details, the SQL operation will fail and we will get an error as response, instead of creating new records in the database.īut there is still a better approach! As you can see, we are providing the data to insert in the record "as-is".
The counterpart is that it can be less clear when you read the code! In addition, note the use of the single quotes to enclose the values passed as strings as part of the SQL statement. Message end tryĪs you can see, the main advantage of this approach is that you write less code. ToString + "')" ) Next Catch e as DatabaseException MessageBox e. ExecuteSQL ( "insert into test(name,surname) values('Name: " + n. The second step is using the method to Connect with the database…and that's all!įor example, this is what we do in the following snippet of code, where the dbsource variable is a property with public scope that has been added to the App object: Some good candidates are a global property with public Scope under a Module or the App object due to the fact that these are global and their scope lasts until we decide to quit the app. Regardless of the targeted platform, we need to follow these simple steps in order to create an in-memory database:Ĭreate a new instance from the SQLiteDatabase class, making sure that the instance will be in scope when we want to use and access the database. In fact, the use of in-memory databases provides a great advantage when implementing some features because they are faster both in retrieving records and in creating, editing or deleting existing data, when compared to those based on files. For 32-bit deployment the total amount of available memory for the app will be around 2 or 3 GB, for 64-bit apps the upper limit will not be a problem at all. Probably the first thing you visualize when talking about databases is a categorized and well structured set of data stored in a physical medium, generally a disk nevertheless -as we saw in the SQLite Basics Tutorial- SQLite also can create in-memory databases, that are only limited by the amount of available RAM in the computer and, mainly, for the selected architecture for the deployment: as 32 or 64-bit. Reporting bugs and making feature requests.DBKit: An easy way to quickly connect a database to your user interface.Considerations when using a database with a web application.SQLiteDatabase for Beginners Quiz Answers.
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