Connecting to MySQL works primarily the same as connecting to other database servers. Starting a transaction varies depending on the database you are using. Xojo is commonly used for creating database applications, but you’ll have to put in a bit of effort on your part to learn how. Lastly, using transactions can improve performance when adding or changing data in the database as the commit operation can be time consuming so if you do it less often (by only committing data that has been added in large chunks) you can improve performance. This prevents people from seeing data before it is ready. Second, for databases that can have multiple users, changes made in a transaction are not usually visible to other users until the transaction is marked as completed (by committing). A failure allows you to revert everything back to its initial state, sort of like an Undo. If an error occurs partway through some changes to several tables, you do not want the data to be missing in some tables. First, it ensures that data integrity is always maintained. When you are using a transaction, changes made to a database are not made permanent until you commit. This is a block of processing that either all completes successfully or none completes successfully. To learn more about general SQL, visit the W3Schools SQL Tutorial.Ĭhanges to a database are made in what is called a transaction. This is optional with some databases, but a semi-colon will be used in code samples for consistency. When you write SQL, as you will see below, it often ends in a semi-colon ( ) character which indicates the "end of the SQL command". This section shows some example of generic SQL that ought to work across most databases. These commands are: SELECT, INSERT, UPDATE, DELETE, COMMIT and ROLLBACK. Regardless, there are several common SQL commands that are always available, even if their specific syntax changes slightly depending on the database you are using. This can make it challenging to switch between database engines (such as SQLite and PostgreSQL, for example) because the SQL used to send commands to the database may be different. But as you create more complex SQL, you'll find that each database has their own slightly different variant of SQL. For simple SQL commands, SQL is often the same across different databases. SQL is the way to send commands to the database to do things such as create tables or get data from tables. The collection of your tables is called the "database schema" or "database design".ĭatabase engines all share a similar command structure, which is called SQL, which stands for Structured Query Language and is often pronounced as "sequel". You can look up the teams for the other players using the same technique. In dynamic languages like Python, the concept of an extension method is unnecessary because classes can be extended without any special syntax. So both Bob and Tom are on the Seagulls team. Looking in the Team table from above, you can see that the team with ID = 1 is the Seagulls. The TypeLib also defines RawBitmap and RawBitmapMask classes that can be used to interact with 3rd party plugins and libraries as well as to avoid inaccuracy of pre-multiplied alpha channels in image processing. For example, you can see that Bob and Tom both have TeamID = 1. TypeLib is Xojo plugin to define some type and support other Einhugur Plugins. It clearly tells you the team to which the player belongs. This column defines the relationship between Player and Team. But in addition, it also has a TeamID column. Notice that the Player table has its own ID column as well. Here is an example of a Player table with sample data: For example, to track the players for each team you would have another table, called Player, that is related to the Team table. And these tables are often related in some way, which is why these are called relational databases. Reporting bugs and making feature requestsĪ database usually consists of many tables.Considerations when using a database with a web application. This code be simplified to: if > 0 then.Īnd if Operator_Convert supported a Nil input parameter as well, then it could be as simple as if someObject.NullableIntProperty > 0 then. This could be completely avoided if extension methods could be called with a Nil input parameter like other languages. Since XOJO doesn’t have built in Object wrappers for the primitivesīecause of this I have created nullable versions of the primitives:įor example I have a class called NullableInteger, but the problem is that you constantly have to null check them if someObject.NullableIntProperty != null & > 0 then. Public static IEnumerable EmptyIfNull(this IEnumerable source) Is this a bug? A short-coming of the language? Can this be fixed? So other language frameworks support extension methods that work even when the object is null/nil.
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