create table payment
(
paymentid number(10) constraint payment_paymentid_pk primary key,
tenantno number (5) not null constraint payment_tenantno_fk references tenant(tenantno),
propid number(5) not null constraint payment_propid_fk references proplookup(proptype),
paydate date default sysdate not null,
amount number(8,2) not null constraint payment_amount_ck check(amount>0),
paidby number(1) not null constraint payment_paidby_ck check(paidby in('cash','chq','credit','bpay')
case paidby 
when 'cash' then paidby = 1
when 'chq' then paidby = 2
when 'credit' then paidby = 3
when 'bpay' then paidby = 4
else paidby = 0
end),
mthof number(2) not null constraint payment_mthof_ck check(mthof between 1 and 12)
);

Error at Command Line:8 Column:101
Error report:
SQL Error: ORA-00907: missing right parenthesis
00907. 00000 -  "missing right parenthesis"

create table payment
(
paymentid number(10) constraint payment_paymentid_pk primary key,
tenantno number (5) not null constraint payment_tenantno_fk references tenant(tenantno),
propid number(5) not null constraint payment_propid_fk references proplookup(proptype),
paydate date default sysdate not null,
amount number(8,2) not null constraint payment_amount_ck check(amount>0),
paidby number(1) not null constraint payment_paidby_ck check(paidby in('cash','chq','credit','bpay')),
case paidby 
when 'cash' then paidby = 1
when 'chq' then paidby = 2
when 'credit' then paidby = 3
when 'bpay' then paidby = 4
else paidby = 0
end as newcolumn,
mthof number(2) not null constraint payment_mthof_ck check(mthof between 1 and 12)
);