I need to find users that have been inserted twice in a table, but with their first name & last name swapped.
e.g. Bob Smith is in the database as
firstname:Bob
lastname:Smith
&
firstname:Smith
lastname:Bob
What's the best query to find those users?
The server runs mysql.
Select
*
FROM UserTable ut
JOIN UserTable ut2 on ut2.firstname = ut.lastname and ut2.lastname = ut.firstname
SELECT
firstname, lastname
FROM
(
SELECT firstname, lastname FROM MyTable -- WHERE firstname <> lastname
UNION ALL
SELECT lastname, firstname FROM MyTable -- WHERE firstname <> lastname
) foo
GROUP BY
firstname, lastname
HAVING
COUNT(*) > 1
SELECT orig.firstname, orig.lastname
FROM yourtable AS orig
INNER JOIN yourtable AS dupes ON orig.firstname = dupe.lastname AND orig.lastname = dupe.firstname
Basically, do a self-join on the user table, but only on the records where the fn/ln dupe-swap occurs.
Related
I want to eliminate the duplicate rows based on email from the table and retrieve all the rows without duplicates.
I have tried using distinct but I'm not getting desired results.
SELECT
DISTINCT Email
FROM
Users
Example Table:
Id
Email
Username
1
sam#gmail.com
sam1122
2
john#gmail.com
john1122
3
sam#gmail.com
sam2233
4
lily#gmail.com
lily#as
What I want to retrieve:
Id
Email
Username
1
john#gmail.com
john1122
2
lily#gmail.com
lily#as
We can try using exists logic here:
SELECT Id, Email, Username
FROM Users u1
WHERE NOT EXISTS (
SELECT 1
FROM Users u2
WHERE u2.Email = u1.Email AND
u2.Id <> u1.Id
);
You can do it using left join :
select u.*
from Users u
left join (
select email, max(id) as Id
from Users
group by email
having count(1) > 1
) as s on s.email = u.email
where s.email is null;
Demo here
Yet another option, if you are using MySQL 8 -
SELECT Id, Email, Username
FROM (
SELECT *, COUNT(*) OVER (PARTITION BY Email) AS cnt
FROM Users
) t
WHERE t.cnt = 1;
SELECT Id, Email, Username
FROM Users
WHERE Email IN (
SELECT Email
FROM Users
GROUP BY Email
HAVING COUNT(*) = 1
)
SELECT id,
Email,
Username,
count(*) AS duplicate_email_count
FROM Users
GROUP BY Email
HAVING duplicate_email_count=1
I have a table like :
name employment_Status email
---- ---- -----
David E David#email.com
John U John#email.com
Michael E Michael#email.com
Steve E Michael#email.com
James U David#email.com
Mary U Mary#email.com
Beth E Beth#email.com
I started by selecting email and count(email):
SELECT email, COUNT(email) AS emailCount
FROM Table
GROUP BY email
HAVING ( COUNT(email) > 1 );
The problem occurred when I tried to include name as well:
SELECT name, email, COUNT(email) AS emailCount
FROM Table
GROUP BY name, email
HAVING ( COUNT(email) > 1 );
I would like to find all people with a duplicate email addresses, (only where both people are employed (E)). However it is returning zero results.
I'd like to be able to display all information for people with duplicate emails, and having employment_Status E. If two people have the same email, but one or both is Unemployed (U), then just ignore.
Could anyone advise?
I think you want exists:
select t.*
from t
where t.employeed = 'E' and
exists (select 1
from t t2
where t2.email = t.email and t2.employeed = 'E' and
t2.name <> t.name
);
Note that this assumes that name (or at least name/email) is unique.
In MySQL 8+, you can use window functions:
select t.*
from (select t.*, count(*) over (partition by t.email) as cnt
from t
where t.employeed = 'E'
) t
where cnt >= 2;
One way would be to use your query as a subquery in FROM clause, and JOIN the result with the main table.
SELECT t.*, d.emailCount
FROM (
SELECT email, employment_Status, COUNT(*) AS emailCount
FROM my_table
GROUP BY email
WHERE employment_Status = 'E'
HAVING emailCount > 1
) d
JOIN my_table t USING(email, employment_Status)
You could also use GROUP_CONCAT(name), if you are fine getiing the names in a (comma) separated string:
SELECT email, COUNT(*) AS emailCount, GROUP_CONCAT(name) as names
FROM my_table
GROUP BY email
WHERE employment_Status = 'E'
HAVING emailCount > 1
The result for your sample data would be:
email emailCount names
-----------------------------------------------
Michael#email.com 2 Michael,Steve
I need to find duplicate uses based on either same email OR first_name, last_name combination OR same birth_date. What I could comfortably try was:
SELECT id, first_name, last_name
FROM users
where id IN (SELECT id
from users
GROUP BY email
HAVING count(*) > 1)
GROUP BY email, id;
The above gives only duplicate email details, but I'm bit confused about handling other conditions based on first_name, last_name combination OR same birth_date as well.
Is it possible to achieve it in a single query?
Try doing a UNION of three separate queries which checks for the three duplicate criteria:
SELECT id
FROM users
GROUP BY id
HAVING COUNT(DISTINCT email) > 1
UNION
(
SELECT id
FROM users t1
INNER JOIN
(
SELECT firstname, lastname
FROM users
GROUP BY firstname, lastname
HAVING COUNT(*) > 1
) t2
ON t1.firstname = t2.firstname AND
t1.lastname = t2.lastname
)
UNION
SELECT id
FROM users
GROUP BY id
HAVING COUNT(DISTINCT birthdate) > 1
Due to Ajax bug I end up having lots of repeated data, where the combination of 2 columns need to be unique.
I simplified the table to name and surname for this question.
Imagine in Table users how can I get the id where name + surname is duplicated.
I have attached a picture.
SELECT id, name, surname FROM users t1 WHERE
EXISTS(SELECT id FROM users t2
WHERE t1.id <> t2.id AND
t1.name = t2.name AND
t1.surname = t2.surname)
Try this
select Id from users u inner join
(SELECT name,surname,count(*) cnt FROM users GROUP BY name,surname
HAVING cnt >1) dup on dup.name = u.name and u.surname = dup.surname
see SQL Fiddle
I have some records in tables A with fields i.e firstname surname, lastname, school, dob
I have another table B with some records and fields i.e firstname, surname, address, club,
I'd like to use the firstname and surname in table B to check if the record exist in table A if it doesnt it should append the record to table A.
I would be glad if you can help me with this
This SQL should do this. Basically, insert from table_b, records with firstname and lastname not existing in table_a.
INSERT INTO table_a (firstname, lastname, address, club)
(
SELECT DISTINCT firstname, lastname, address, club FROM table_b
WHERE (firstname, lastname) NOT IN (SELECT firstname, lastname FROM table_a)
)
Try this query -
INSERT INTO table_a(firstname, lastname)
SELECT b.firstname, b.lastname FROM table_b b
LEFT JOIN table_a a ON b.firstname = a.firstname AND b.lastname = a.lastname
WHERE a.firstname IS NULL AND a.lastname IS NULL;