simple recursive query

Question

I have 2 tables as follows (sample data shown):

TableName: A
ID              Type
1  Bug
2  Requirement
3  Task
4  Specification
5  Bug
6  Specification
7  Production Issue
8  Production Issue
9  Bug
10          Task

Tablename: B
ID  RelatedID
1  2
1  7
5  8
5  4
9  6
9  10

I want to fetch all the bugs that have atleast one related production issue or bugs that have no related production issue.

Expected output will be as shown below (since these are the bugs with at least one related production issue)

output
1
5

Answer 1

Aliases are the way to go here

SELECT pri.Type AS 'Primary Type', rel.Type AS 'Related Type' 
FROM A AS pri 
   INNER JOIN B ON B.ID = pri.ID
   INNER JOIN A AS rel ON B.RelatedID = rel.ID
WHERE pri.Type = 'Bug' AND rel.Type = 'Production Issue;