如何从parse.com中的多个表中检索数据

Question

I put my data in 3 tables(Links, Images and PDF)

each table has columns(university, faculty, grade, and description,...)

I want to retrieve description column in the 3 tables.

where university, faculty, and grade equal to certain values.

and sort them with creation date.

how can I perform that query in parse?

Answer 1

I'm not familiar with Android, but I'm pretty sure Parse does not support "Join" in the way a SQL database does. You could nest the queries, performing the next one in the previous one's completion block.

However, if you regularly want to get data from those 3 tables, I'd suggest you make it 1 table instead, with a column "Content" instead of Link/Img/PDF. Images and PDFs would probably be stored as PFFiles anyway, and you can put link as either its own string column or putting it in a file. You could also add a column "type" if you want to be able to query a specific type, or just keep track of which columns contains which data.

Then you could query the "Content" class, on the keys you want.

Answer 2

I think this link might help you https://parse.com/docs/js/guide#relations and it is quite simple and nicely explained . You can't do it directly in the database, though.