结合MySQL表与查询UNION或JOIN？

Question

brand new to complex mysql queries. I have a database schema that includes a pair of tables that I need to combine:

In the first table avatars, I have columns user_id , url , and name, with a single row for each unique user_id. In the second table interpretations I have user_id and scan_index plus 3 other fields. I'd like to generate a mysql result that matches a specific scan_index from interpretations, includes all columns from this table and additional corresponding fields url , and name from avatars. Should I be using JOIN or UNION to do this query?

Answer 1

JOIN is used to combine both tables on the basis of column values (here in your case, i guess, its user_id), your query can be something like this :

SELECT url, name, scan_index,...
FROM avatars
LEFT JOIN interpretations 
ON avatars.user_id = interpretations.user_id
WHERE interpretations.scan_index = *your_specific_value*

Answer 2

You need to use join . To explain it very simply, a join combines 2 tables by placing the data from the 2 tables next to each other, while a union combines 2 queries by placing the data below each other.