1
vote
1answer
36 views

JOIN to read first table and get possible relationship in the second table

Consider a main table as CREATE TABLE groups ( group_id int(11) NOT NULL AUTO_INCREMENT, group_title varchar(255), PRIMARY KEY(group_id) ) ENGINE=InnoDB and a second table for relationship as ...
2
votes
3answers
322 views

Express union which is dependent on other results

I would like to make a union of two tables that are actually in a hierarchical constellation. How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship. ...