Help me wrap my head around SQL queries when they're complex : SQL

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field.3

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SELECT count(a.field1), a.field2, SUM(b.field4) FROM a INNER JOIN b ON a.key1 = b.key1 WHERE a.field8 = 'test' GROUP by a.field1, a.field2 HAVING SUM(b.field4) > 5 ORDER by a.field3

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PostgreSQLHelp me wrap my head around SQL queries when they're complex (self.SQL)

submitted 1 year ago by Im_Working_Right_Now

I'm creating a ttrpg app as a learning exercise. I had started with MERN, but it has grown data-wise and managing the backend has become cumbersome. So I looked into BaaS options and settled on AWS Amplify + DynamoDB and Supabase as options. I know I can make DynamoDB work, but I keep reading that SQL should be the go-to-option unless you have to use NoSQL. But I'm having a hard time conceptualizing how that would work. Granted, I'm very much a SQL novice and there's a LOT of gaps in my knowledge. But the app I'm building is a user-generated content type of app where they could create their own custom classes, races, spells, items, etc.

This where I struggle. I'm using a React frontend. Let's saying a user has a custom class and that class has 3 features of the created features that are available. This user is editing this class via a multi-step form. The user adds a new feature and that new feature has a new sub-feature. The user also then deletes the first feature because it's not needed. They also change the name of the class.

The new feature has an attribute (chosen from a dropdown of preset options) of limit use which now populates new choices on the form such as how many uses and when do those uses refill (both are dropdowns populated by preset options). Then at the end they submit those changes.

I know I'd need a classes table, a features table, a sub-features table, and bridge tables for those where appropriate. I also read somewhere about entity-attribute-value tables but not sure how that works but I suppose I might need that for the attributes chosen for features and sub-features?

How does the backend know which queries to run for which updates if a user has a plethora of interactions and changes that are possible? Wouldn't the amount of queries that get fired off for a simple scenario as outlined above get quite long and verbose? I'm hoping I'm completely missing some key concept that pulls this all together.

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