I have the following tables:
Table 1 : Contacts
Fields : id first_name
Values :
1 Reeta
2 Rohan
3 John
Table 2 : email (it contains contact_id of contacts table)
Fields : id contact_id email_address
Values :
1 1 r#gmail.com
2 2 r#gmail.com
3 3 j#gmail.com
I want to display all duplicates by email. Like this:
cont_id first_name email_address
1 Reeta r#gmail.com
2 Rohan r#gmail.com
Here is my query :
select contact_id
from contacts
where email_address IN (
SELECT S.email_address
FROM contacts R
INNER JOIN email
ON R.id = S.contact_id
Group By email_address
Having Count(S.id) > 1
);
The query takes long time to execute with large number of records. However the inner query works faster but not the outer one. Please Help.
I would move your INNER JOIN outside of your subquery.
SELECT
c.contact_id,
c.first_name,
e.email_address
FROM contacts c
INNER JOIN email e ON c.id = e.contact_id
WHERE e.email_address IN (
SELECT email_address
FROM contacts
GROUP BY email_address
HAVING COUNT(id) > 1
);
You could also implement MySQL's EXPLAIN to get a better idea what's choking your query.
Another way to do it, which should be quicker, is something like this:
select email.email_address, group_concat(contacts.contact_id)
from contacts inner join email on contacts.contact_id=email.contact_id
group by email.email_address
having count(contacts.contact_id) > 1;
Now, you're getting exactly what you want; the only thing is, the contact IDs will be concatenated as a comma-separated string. But you'll know which email addresses are non-unique.
You should also have indexes on contact_id in all tables (because you join on these fields), and probably email_address as well (since you search on it).
Related
I have three tables. One with notes Notes, one with users Users, and one a relational table between users and notes NotesUsers.
Users
user_id first_name last_name
1 John Smith
2 Jane Doe
Notes
note_id note_name owner_id
1 Math 1
2 Science 1
3 English 2
NoteUsers
user_id note_id
1 1
2 1
2 2
2 3
Hopefully, from the select statement you can tell what I'm trying to do. I am trying to select the notes that user_id = 2 has access to but doesn't necessarily own, but also along with this I'm trying to get the first and last name of the owner.
SELECT Notes.notes_id, note_name
FROM Notes, NotesUsers
WHERE NotesUsers.note_id = Notes.note_id AND NotesUsers.user_id = 2
JOIN SELECT first_name, last_name FROM Users, Notes WHERE Notes.owner_id = Users.user_id
My problem is that because the WHERE clause for first_name, and last_name versus that for notes are different, I don't know how to query the data. I understand that this is not how a JOIN works and
I don't necessarily want to use a JOIN, but I'm not sure how to structure the statement, so I left it in there so that you can understand what I'm trying to do.
You can join Notes with NoteUsers to check for access and with Users to add the user's details to the result:
SELECT n.noted_id, n.note_name, u.first_name, u.last_name
FROM Notes n
JOIN NoteUsers nu ON n.noted_id = nu.note_id AND nu.user_id = 2
JOIN Users u ON n.owner_id = u.user_id
you need here to use a query inside the main query. MySQL will return first all the note_id that the user with user_id = 2 has access to from NoteUser, then well build the outer query to return the first_name and the last_name of the owner.
SELECT u.first_name, u.last_name, n.note_name, n.note_id
FROM Notes AS n
LEFT JOIN Users AS u ON u.user_id = n.owner_id
WHERE n.note_id IN
(SELECT nu.note_id FROM NoteUser WHERE nu.user_id = 2)
i'm running into a complex problem, the data in a db has three tables.
First_DB
-- default_users
id username email password
1 Timbog Timbog#mail.com vads7y3kkjdfa
2 Marta Marta#mail.com vads7y3kkjdfa
-- default_album
album_id album_name default_user_id
1 Name_Tim 1
3 Katarina 2
-- default_album_img
img_id image_file album_id
3 1320229733.jpg 1
4 3320229733.jpg 3
Second_DB
--users
user_id user_name user_email user_pass user_image
1 Timbog Timbog#mail.com vads7y3kkjdfa 1320229733.jpg
2 Marta Marta#mail.com vads7y3kkjdfa 3320229733.jpg
The approach i used to solve this problem is to first fetch all data by inner join, should i use full outer join and insert the required field to my table, the following query is actual by which i'm trying to make it wor:
INSERT INTO bbpin.users ( user_name, user_pin, user_email, user_password, user_img)
SELECT default_users.username, default_users.bb_pin, default_users.email, default_users.password
FROM bbmpins_pins.default_users
INNER JOIN bbmpins_pins.default_album_images
ON default_album_images.album_id = default_users.id;
i miss the thing how do i compare two table's id in this join maybe? or this query is all wrong by approach?
By two tables which are sepearte in First_DB there could be multiple record how do we trunk them to last entry only ?
Thanks
It looks like you are attempting to retrieve all rows from the default_users table. And along with each row, also return the corresponding row(s) from default_album table. And along with that, the corresponding row(s) from default_album_img table.
Given the example data, a query using inner joins would return the specified result:
SELECT u.id AS user_id
, u.username AS user_name
, u.email AS user_email
, u.password AS user_pass
, i.image_file AS user_image
FROM default_users u
JOIN default_album a
ON a.default_user_id = u.id
JOIN default_album_img i
ON i.album_id = a.album_id
That query will work for the example data.
But, if there is a row in default_user which doesn't have a matching row in default_album, then an inner join won't return that row:
-- default_users
id username email password
3 branstark bran#winterfell warg2
Or, if there are two or more rows in default_album that match a given user, then the query will return two copies of the row from default_user...
-- default_album
album_id album_name default_user_id
1 Tim2 1
Without a specification of what is to be returned in those cases, we can't recommend a query.
I don't see anything wrong with your current approach using a JOIN but could modify it a bit to be more readable and also you will have to join the relation table
INSERT INTO bbpin.users (user_id, user_name, user_pin, user_email, user_password, user_img)
SELECT du.id,
du.username,
du.bb_pin,
du.email,
du.password,
dai.image_file
FROM bbmpins_pins.default_users du
JOIN bbmpins_pins.default_album da ON du.id = da.default_user_id
INNER JOIN bbmpins_pins.default_album_images dai
ON dai.album_id = da.album_id;
I am using MySQL and database server and I have two tables one is for customer and another for customer_contacts.
Here are the table structures:
customer(
id(pk, ai)
name
email
)
and
customer_contacts(
id(ai)
customer_id
first_name
last_name
)
Now my question is:
lets say I have one customer has many customer_contacts like this
customer
id name email
1 john john#example.com
and customer_contacts is like this (first row)
id customer_id first_name last_name
1 1 john doe
2 1 johnp pual
like this
So here I want to get all the contact details count for the id john. So can some one tell me how to get that?
Any help and suggestions will be really appreciable. Thanks
If the id is already known (as suggested by the question, it would be a plain
SELECT COUNT(*) from customer_contacts
WHERE customer_contacts.id = 1;
You just need to know the number of contactacs for the customer John, right?
SELECT COUNT(*)
FROM customer cus INNER JOIN customer_contacts con ON cus.id = con.customer_id
WHERE cus.name = 'john'
Nevertheless, It would be better if you know the id of John. Your query would be this:
SELECT COUNT(*)
FROM customer_contacts
WHERE customer_id = 1
Simply join both tables and use count() with group by c.id use where to filter records
select c.*,
count(*) total_contacts
from customer c
left join customer_contacts cc on(c.id = cc.customer_id)
group by c.id
Fiddle Demo
I am not a databases guy,but I have been given the "fun" job of cleaning up someone else's database. We have many duplicate record in our databases and some of customers are getting double or triple billed every month.
Given the following Database example
:
Table: Customers
ID Name Phone DoNotBill
1 Acme Inc 5125551212 No
2 ABC LLC 7138221661 No
3 Big Inc 4132229807 No
4 Acme 5125551212 No
5 Tree Top 2127657654 No
Is it possible to write a query that Identifies the all duplicate phone numbers (in this case records 1 and 4) and then marks and duplicate records yes by updating the DoNotBill column. But leaves the first record unmarked.
In this example case we would be left with:
ID Name Phone DoNotBill
1 Acme Inc 5125551212 No
2 ABC LLC 7138221661 No
3 Big Inc 4132229807 No
4 Acme 5125551212 Yes
5 Tree Top 2127657654 No
something like this?
UPDATE
customers cust,
(SELECT
c1.ID,
c1.name,
c1.phone,
c1.DoNotBill
FROM customers c
LEFT JOIN
(SELECT
cc.ID
FROM customers cc
) as c1 on c1.phone = c.phone
) dup
SET cust.DoNotBill = 'Yes' WHERE cust.id=dup.id ;
To begin with I assume that the DoNotBill column only has two possible values; yes and no. In that case it should be bool instead of varchar, meaning it would be either true or false.
Furthermore I don't get the meaning of the DoNotBill column. Why wouldn't you just use something like this?
select distinct phone from customers
SQL SELECT DISTINCT
That would give you the phone numbers without duplicates and without the need for an extra column.
This depends on ur data amount
You can do it in steps and make use some tools like excel...
This qrt
SELECT a.id,b.id,a.phone FROM clients a , clients b WHERE
A.phone =b.phone
And a.id!=b.id
The result is all duplicated records.
Add
Group by a.phone
And u will get 1 record for each 2 duplicates.
if you like the records and they are whT u need. ChNge select to select a.id and
Use this qry as subqry to an update sql statement
UPDATE clients SET billing='no' WHERE id IN ( sql goes here)
UPDATE customers c SET c.DoNotBill="Yes";
UPDATE customers c
JOIN (
SELECT MIN( ID ) ID, Phone
FROM customers
GROUP BY Phone
) u ON c.ID = u.ID AND c.Phone = u.Phone
SET c.DoNotBill="No";
That way not only duplicates are eliminated, but all multiple entries are dealt with.
I have table users and another table premium_users in which I hold the userid and the date when he bought premium membership.
How can I use mysql join , so that in a single query I can select all the columns from the table users and also know for each premium user the date he joined on.
USERS:
ID USERNAME
1 JOHN
2 BILL
3 JOE
4 KENNY
PREMIUM USERS:
ID USERID DATE
1 2 20/05/2010
2 4 21/06/2011
And the final table (the one that will be returned my the query) should look like this:
ID USERNAME DATE
1 JOHN
2 BILL 20/05/2010
3 JOE
4 KENNY 21/06/2011
Is it ok for some rows to have the DATE value empty?
How can I check if that value is empty? $row['date']=='' ?
EDIT:
This was only an example, but the users table has much more columns, how can I select all from users and only date from premium_users without writing all the columns?
select u.*, pu.DATE
from USERS u LEFT OUTER JOIN PREMIUM_USERS pu on
u.ID = pu.USERID
You can check if a row is empty with:
if (!$row['DATE'])
{
...
}
select USERS.ID, USERS.USERNAME, PREMIUM_USERS.DATE
from USERS
join PREMIUM_USERS on USERS.ID = PREMIUM_USERS.ID
order by USERS.ID
This is mssql syntax, but it should be pretty similar...
select *
from users u
left join premiumUsers p
on u.id = p.id
order by u.id asc
SELECT A.*, B.DATE
FROM USERS A
LEFT JOIN PREMIUIM_USERS B on A.ID=B.USERID
EDITED
It might be easier to have it all in one table. You can have nullable fields for isPremium(t/f) and premiumDate. you actually dont even need the isPremium field. just premiumDate if its null they are not premium and if it has value they are premium user and you have the date they joined.