Using synchronous and asynchronous database operations

Previous sections have described common database operations such as retrieving, inserting, updating, and deleting data, as well as creating a database file and tables and other objects within a database. The examples have demonstrated how to perform these operations both asynchronously and synchronously.

As a reminder, in asynchronous execution mode, you instruct the database engine to perform an operation. The database engine then works in the background while the application keeps running. When the operation finishes the database engine dispatches an event to alert you to that fact. The key benefit of asynchronous execution is that the runtime performs the database operations in the background while the main application code continues executing. This is especially valuable when the operation takes a notable amount of time to run.

On the other hand, in synchronous execution mode operations don't run in the background. You tell the database engine to perform an operation. The code pauses at that point while the database engine does its work. When the operation completes, execution continues with the next line of your code.

A single database connection can't execute some operations or statements synchronously and others asynchronously. You specify whether a SQLConnection operates in synchronous or asynchronous when you open the connection to the database. If you call SQLConnection.open() the connection operates in synchronous execution mode, and if you call SQLConnection.openAsync() the connection operates in asynchronous execution mode. Once a SQLConnection instance is connected to a database using open() or openAsync(), it is fixed to synchronous or asynchronous execution.