Updating rows in sql

Firebase uses references to pull your data, for example, if you want to pull the "National Pizza Day" event you'll do something like this: That will bring the entire event information, so if all you need is the event name date then this is not a really great idea, you're going to be pulling a ton more data than you need to if those inside lists start growing. ) for your data, but it's a really bad idea to go that deep, imagine only needing the event name and pulling instead the name a list of 5,000 people that attended to the event (and National Pizza Day?

updating rows in sql-85

We will revert to the key-preserved join and this time our MERGE should be successful.

Before we begin, we will create two scratch tables to work with; a source table and a target table.

For example, if you're building an event management app (...which I once had to do for my wife : P ) you might be thinking about how to store your users, the events you're creating, and the relationship between them. It depends on your database, your goals, and especially on your view, for example: You have an event view, where you're seeing the information about that event, inside the view, you have a guest list, that shows just that, a list of the guests who attended the event.

You might be thinking something like this: so we know the user with the ID of "ebratt Jorge" went to the event This is actually a great start, but if you want to get more information about these users (and you'd probably want) you'd have to use the user's ID to query his information. If you're coming from an SQL background you probably know about normalization (avoid duplicates, structure tables, etc). You're probably not going to need much information about the guests at that point, so instead of doing an extra query, you could do something like this: That way you have all the data you need about the guests, so you won't have to call the database a second time to display the guest list.

In versions prior to 9i, we would have to code this scenario either in separate bulk SQL statements or in PL/SQL.

We will compare MERGE to these methods later in this article.This article introduces the new MERGE SQL command (sometimes referred to as "UPSERT").MERGE is a DML command that enables us to optionally update or insert data into a target table, depending on whether matching records already exist.This is really great for flexibility but doesn't really help us ensure data integrity. In this post, I'm going to do my best to guide you in how to structure your data in Firebase, so allow ultra fast reads, minimal querying, and how you'll accomplish a common SQL query just restructuring your data.We'll break it into 3 parts: One of the best ways to ensure your app is going to stay performant is to keep your database connection "clean", meaning that there isn't too much clutter, too many database calls for things that you don't really need to.We will replace the two-part SQL solution with a PL/SQL loop that will attempt an update first and insert only if the update affects no rows.

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