sql: join two tables and display records even if they are in first table and not in the second table - sql

Question

I don't know if the title justifies the question but
i have 2 tables table A a and table B b. I am inner joining these two tables with
on (a.msisdn = b.frmsisdn or a.msisdn = b.tomsisdn)
in table A i have all the details of the users like names, msisdn, regdate, status, address etc
in table B i have user's transaction reports like timestamp, frmsisdn, tomsisdn, reference, amounts etc
Both tables have MSISDN as common but in Table A it is named as MSISDN and in Table B this can either be in FRMSISDN or TOMSISDN or will not be in any of the fields(usually users with no transactions).
But when i try to do like this, the report i am getting is not displaying the users who are in Table A with no entries in Table B, basically registered in the database but did not do any transactions as all.
Can someone tell me how do i include the MSISDN from Table A in the report even if they dont have an entry in Table B
Here is the query i am trying
select mai.msisdn, mai.firstname, mai.lastname, type as account_type,
alias as nickname, mai.regdate, mai.status,
amount as balance, count(trai.referenceid) as number_of_transactions,
sum(trai.amount) as sum_of_transactions from tableA mai
inner join tableC stk
on mai.msisdn = stk.msisdn
inner join tableB trai
on (mai.msisdn = trai.tomsisdn or mai.msisdn = trai.frmsisdn)
where trai.status = 0
and stk.walletid = 0
group by mai.msisdn, mai.firstname, mai.lastname, mai.type,
mai.alias, mai.regdate, mai.status,
stk.amount;

Answer 1

If you need all the entry of table A also when there si no enty in table B the use LEFT join for table B
select
mai.msisdn
, mai.firstname
, mai.lastname
, type as account_type
, alias as nickname
, mai.regdate
, mai.status
, amount as balance
, count(trai.referenceid) as number_of_transactions
, sum(trai.amount) as sum_of_transactions
from tableA mai
left join tableB trai on (mai.msisdn = trai.tomsisdn or mai.msisdn = trai.frmsisdn)
inner join tableC stk on mai.msisdn = stk.msisdn
where trai.status = 0
and stk.walletid = 0
group by
mai.msisdn
, mai.firstname
, mai.lastname
, mai.type
, mai.alias
, mai.regdate
, mai.status
, stk.amount;
or if you problem is limited but the inner join for table C
try using inner join for this table too
select
mai.msisdn
, mai.firstname
, mai.lastname
, type as account_type
, alias as nickname
, mai.regdate
, mai.status
, amount as balance
, count(trai.referenceid) as number_of_transactions
, sum(trai.amount) as sum_of_transactions
from tableA mai
left join tableB trai on (mai.msisdn = trai.tomsisdn or mai.msisdn = trai.frmsisdn)
left join tableC stk on mai.msisdn = stk.msisdn
where trai.status = 0
and stk.walletid = 0
group by
mai.msisdn
, mai.firstname
, mai.lastname
, mai.type
, mai.alias
, mai.regdate
, mai.status
, stk.amount;

Answer 2

Try
select mai.msisdn, mai.firstname, mai.lastname, type as account_type,
alias as nickname, mai.regdate, mai.status,
amount as balance, count(trai.referenceid) as number_of_transactions,
sum(trai.amount) as sum_of_transactions
from tableA mai
inner join tableC stk
on mai.msisdn = stk.msisdn
and stk.walletid = 0
left join tableB trai
on (mai.msisdn = trai.tomsisdn or mai.msisdn = trai.frmsisdn)
and trai.status = 0
group by mai.msisdn, mai.firstname, mai.lastname, mai.type,
mai.alias, mai.regdate, mai.status,
stk.amount;
See the difference how (at what stage) predicate is applied in LEFT JOIN .. ON and in WHERE.