Case with multiple records - mysql

Question

I have a data set which looks like this:
id No_trans Bank
1 2 VISA
1 1 PAYPAL
2 3 MASTERCARD
3 1 MASTERCARD
3 4 PAYPAL
4 1 PAYPAL
What I need to do is if id has PAYPAL, change it to another bank, for example.
For id = 1, PAYPAL should be as VISA, but for id = 3, it should be MASTERCARD, however, for id = 4, it should be PAYPAL because it doesn't have another Bank record.
select id ,count(No_trans) ,
case Bank when PAYPAL then VISA
when PAYPAL then MASTERCARD
else
PAYPAL
end as bank
from table
Grouping by 1 and 3
is not going to work, because I need to change it depending on which other record has the same id bank.
If this ID has a bank different from PAYPAL, use it for other records with the same ID, if not, use it as it is.
create temporary table t1
(
ID INT
, no_trans int
, bank varchar (255)
);
INSERT INTO t1 values
(1, 2 , 'VISA'),
(1 , 1 , 'PAYPAL'),
(2, 3 , 'MASTERCARD'),
(3 , 1 , 'MASTERCARD'),
(3, 4 , 'PAYPAL'),
(4 , 1 , 'PAYPAL');
select * from t1
where id = 1
return
'1','2','VISA'
'1','1','PAYPAL'
I need
'1','2','VISA'
'1','1','VISA'
for
select * from t1
where id = 3
should be
ID, no_trans, bank
3, 1, MASTERCARD
3, 4, MASTERCARD
for
select * from t1
where id = 4
ID, no_trans, bank
4, 1, PAYPAL

Answer 1

You can use aggregation:
select id,
coalesce(max(case when Bank <> 'PayPal' then Bank end),
max(Bank)
)
from t
group by id;
If you want the original rows, then perhaps a subquery is simpler:
select t.*,
(select t2.bank
from t t2
where t2.id = t.id
order by (t2.bank <> 'PayPal) desc
limit 1
) as new_bank
from t;

Answer 2

Try the following:
select
ID,
no_trans,
If (id = 1 and bank = 'PAYPAL', 'VISA',bank)as bank
from t1
where id = 1
For Id = 3
select
ID,
no_trans,
If (id = 3 and bank = 'PAYPAL', 'MATERCARD',bank) as bank
from t1
where id = 3;
If you need all of them combined:
select
ID,
no_trans,
If (bank = 'PAYPAL',If(id = 1,'VISA',If(id=3,'MASTERCARD',bank)),bank) as bank
from t1;
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