I have a SQL DB that contains multiple relational tables. There are some fields in the master table that reference another table multiple times. For example, say I have a database of salesmen who are responsible of sales for multiple states. My database has fields for State1, State2, and State3 all of which map back to a States table. I can't figure out for the life of me how to write a query to return a record with all the enumerated states. If I only needed one State field, I know I would do:
SELECT Master.Name, State.Enumeration AS 'State'
FROM MasterTable Master, StateTable State
WHERE Master.State1 = State.ID;
How can I expand this for all my State fields?
Thanks.
Returning a column from each of the unique joins to the states:
select m.Name, s1.Enumeration as State1, s2.Enumeration as State2, s3.Enumeration as State3
from MasterTable m
left join StateTable s1 on m.State1 = s1.ID
left join StateTable s2 on m.State2 = s2.ID
left join StateTable s3 on m.State3 = s3.ID
Returning 1 column of all the states from the 3 joins:
select m.Name, ISNULL(s1.Enumeration + ',','')
+ ISNULL(s2.Enumeration + ',','')
+ ISNULL(s3.Enumeration,'') as Enumeration
from MasterTable m
left join StateTable s1 on m.State1 = s1.ID
left join StateTable s2 on m.State2 = s2.ID
left join StateTable s3 on m.State3 = s3.ID
There is also column-queries...
select m.Name,
ISNULL((select Enumeration from StateTable where ID = m.State1),'') as State1,
ISNULL((select Enumeration from StateTable where ID = m.State2),'') as State2,
ISNULL((select Enumeration from StateTable where ID = m.State3),'') as State3
from MasterTable m
You need to use table aliases in order to join multiple copies of the same table:
SELECT m.Name,
s1.Enumeration AS 'State1',
s2.Enumeration AS 'State2'
FROM MasterTable m
LEFT JOIN StateTable s1 = s1.id = m.state1
LEFT JOIN StateTable s2 = s1.id = m.state2
An INNER JOIN requires that data is present - if not, the entire record is excluded. A LEFT JOIN is safer, like if the state1/2/3/etc allows NULLs...
select tbl_book_con1.city,con1,tbl_book_destination.city,destination,labar_char,tbl_book_c_from.city,c_from,tbl_book_c_to.city,c_to,tbl_book_payment.city,paymentid from tbl_booking tbb_bookinner join tbl_master tbl_book_con1 on tbl_book_con1.id = tbb_book.con1 inner join tbl_master tbl_book_destination on tbl_book_destination.id = tbb_book.con1 inner join tbl_master tbl_book_c_from on tbl_book_c_from.id = tbb_book.con1 inner join tbl_master tbl_book_c_to on tbl_book_c_to.id = tbb_book.con1 inner join tbl_master tbl_book_payment on tbl_book_payment.id = tbb_book.con1
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