Finding some same values within each ID - sql

Question

I have this kind of data, with ID column identifying potential duplicates,
in this data same Id means it is a same customer, what I want to do is show that 456 account not required as it is covered under account 123, is there a way I can do that on SQL or tableau? I want to show all accounts like 456 within ID group.

Answer 1

with cte as (
select min(customer_account) as account, id --This query will get the first account for each ID
from table
group by ID
)
select customer_account, id --this will show, for each id, all the 'duplicated' customers
from table
where customer_account not in (select account from cte)
the result should be:
456 1
789 1
ID with just one customer ID won't appear

Answer 2

Write a SQL query that selects the minimum Customer value for each ID. Join that dataset back to the original table where the original table's Customer value is greater than the minimum for each corresponding ID. Here is a SQLFiddle example:
http://www.sqlfiddle.com/#!9/93296f/20
Here is the DDL used to recreate your question:
CREATE TABLE Table1
(`Id` int, `Customer_Account` int, `City` varchar(9));
INSERT INTO Table1
(`Id`, `Customer_Account`, `City`)
VALUES
(1, 123, 'London'),
(1, 123, 'Paris'),
(1, 456, 'Paris'),
(1, 456, 'Mumbai'),
(1, 123, 'Mumbai'),
(1, 789, 'Singapore');
Here is the DML used to show the duplicate Customer Accounts. Query 3 should give you the final results.
-- Query 1: Find the First Account for each Customer
select `Id`,
min(`Customer_Account`) as 'First Account by Customer'
from Table1 group by `Id`;
-- Query 2: Find the First Account for Each Customer by City
select `Id`,
min(`Customer_Account`) as 'First Account by City',
`City`
from Table1
group by `Id`, `City`;
-- Query 3: Find the Duplicate Customer Accounts by ID
select distinct
A.Id,
A.Customer_Account as 'Duplicate Account by Customer',
FirstAcctList.First_Account
from Table1 A
join (
select
`Id`,
min(`Customer_Account`) as 'First_Account'
from Table1 group by `Id`) as FirstAcctList
on FirstAcctList.First_Account <> A.Customer_Account;