Select All customers with exact name and birthdate - mysql

Question

I want to select all the customers that have the same name and birth date on mysql table.
my query right now is close, but it seems to have a flaw:
SELECT
id,
customer.name,
date
FROM
customer
INNER JOIN (
SELECT
name
FROM
customer
GROUP BY
name,date
HAVING
COUNT(id) > 1
) temp ON customer.name = customer.name
ORDER BY
name;

Answer 1

Return a customer if there EXISTS another one with same name and date, but other id:
SELECT
id,
name,
date
FROM
customer c1
where exists (SELECT 1 from customer c2
where c2.name = c1.name
and c2.date = c1.date
and c2.id <> c1.id)
JOIN version:
SELECT
c1.id,
c1.name,
c1.date
FROM
customer c1
JOIN customer c2
ON c2.name = c1.name
and c2.date = c1.date
and c2.id <> c1.id

Answer 2

You can do it using EXISTS expression:
SELECT
id,
customer.name,
date
FROM customer c
WHERE EXISTS (
SELECT *
FROM customer cc
WHERE cc.name=c.name AND cc.date=c.date AND cc.id <> c.id
)
The meaning of this query can be derived by pretending it's plain English: we are looking for all customers c for which there exists another customer cc with the same name and birth date, but different id.

Answer 3

Something like this should do it:
select
c1.*
from
customer c1
join customer c2 on
c1.name = c2.name
and c1.birth_date = c2.birth_date
and c1.id != c2.id
order by name, birth_date, id
;
And here's the full example:
drop table customer;
create table customer (
id int,
name varchar(64),
birth_date date
);
insert into customer values (1, 'Joe', '2001-01-01');
insert into customer values (2, 'Joe', '2001-01-02');
insert into customer values (3, 'Joe', '2001-01-03');
insert into customer values (4, 'Jim', '2001-01-01');
insert into customer values (5, 'Jack', '2001-01-01');
insert into customer values (6, 'George', '2001-01-01');
insert into customer values (7, 'George', '2001-01-02');
insert into customer values (8, 'Jeff', '2001-01-02');
insert into customer values (10, 'Joe', '2001-01-01');
insert into customer values (60, 'George', '2001-01-01');
select * from customer;
select
c1.*
from
customer c1
join customer c2 on
c1.name = c2.name
and c1.birth_date = c2.birth_date
and c1.id != c2.id
order by name, birth_date, id
;
+ ------- + --------- + --------------- +
| id | name | birth_date |
+ ------- + --------- + --------------- +
| 6 | George | 2001-01-01 |
| 60 | George | 2001-01-01 |
| 1 | Joe | 2001-01-01 |
| 10 | Joe | 2001-01-01 |
+ ------- + --------- + --------------- +
4 rows

Answer 4

Assuming a table with only id, name and date, you can expand it after that.
The solution is going to be in using an aliased join or an exists clause.
First some code to setup a temporary table with some values for us to query against.
--Drop Temporary Test Table if it exists
IF OBJECT_ID('tempdb.dbo.#Customers_Test', 'U') IS NOT NULL
DROP TABLE #Customers_Test;
--Create a Temporary Test Table
CREATE TABLE #Customers_Test
(
[id] [int] IDENTITY(1,1) NOT NULL,
[name] [varchar](50) NULL,
[date] [datetime] NULL,
CONSTRAINT [PK_Customers_Test] PRIMARY KEY CLUSTERED
(
[id] ASC
)
WITH
(
PAD_INDEX = OFF,
STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON
) ON [PRIMARY]
) ON [PRIMARY]
--Put some temporary values into the table
INSERT INTO #Customers_Test(name, [date])
VALUES ('Joe', GETUTCDATE()),
('Mark', GETDATE()),
('Dan', '1/1/1990'),
('Dan', '1/1/1990')
Now for the actual selection styles, there are several ways to do this depending on mostly preferences, if this query had become more complex there may have been a significant run time advantage of one over another.
--First Select Version
SELECT #Customers_Test.id,
#Customers_Test.name,
#Customers_Test.[date]
FROM #Customers_Test
WHERE EXISTS (
SELECT 1
FROM #Customers_Test Duped_Customers
WHERE Duped_Customers.name = #Customers_Test.name
AND Duped_Customers.[date] = #Customers_Test.[date]
AND Duped_Customers.id <> #Customers_Test.id
)
Another way:
--Second Select Version
SELECT #Customers_Test.id,
#Customers_Test.name,
#Customers_Test.[date]
FROM #Customers_Test
INNER JOIN #Customers_Test AS Duped_Customers
ON #Customers_Test.name = Duped_Customers.name
AND #Customers_Test.[date] = Duped_Customers.[date]
AND #Customers_Test.id <> Duped_Customers.id
One Final Way:
--Third Select Version ( Similar to your current logic).
SELECT #Customers_Test.id,
#Customers_Test.name,
#Customers_Test.[date]
FROM #Customers_Test
WHERE #Customers_Test.name IN (
SELECT name
FROM #Customers_Test Duped_Customers
GROUP BY name, [date]
HAVING COUNT(name) > 1
)