As soon as I apologize because I do not know or be able to explain exactly trouble.
How get value from table user_address.
how to pass user ID in the second "select".
select id, name, age,
(select address
from user_address
where user_id = ??user.id
ORDER BY address_name
LIMIT 1) AS address
from user
As an addendum to what already exists, you should probably not be relying on the specific order of rows in the database to give some sort of semantic meaning. If you have some better way of identifying which address you're after, you could use a join, such as:
select id, name, age, address
from user
inner join user_address
on user.id=user_address.user_id
where address_type='Home'
(adjust the where clause to whatever)
I assumed that you want to get something like the first address for a user
(each user may have a couple of addresses)
-there is another option that you want to find the first persone that lives in a given address (The solution below doesn't address this case)
SELECT u.id,u.name,u.age,a.ua as address
FROM
(
SELECT * FROM users
) u
INNER JOIN
(
SELECT userID, MIN(address) AS ua
FROM user_address
GROUP BY userID
) a
on u.id = a.userID
The syntax is for SQLServer - if you use MSAccess(you can use First and not min)
Hope it helps
Asaf
Related
I'd appreciate any assistance people could provide with this one. I've tried to follow a couple of other posts (GROUP BY to combine/concat a column), but when I do this, it combines everything.
I have a table in SQL that holds contact data. Some contacts in the database have the same email address, particularly admin#, accounts#, etc. We also have a list of contact preferences for each contact: Emergency Contact, Accounts, WHS, etc. I'm trying to select the results of the table, but only one row per email address.
My data looks like this:
However, I'd like it to group the rows together that have the same email address (I don't care about the names). I'd also like it to look at the contact preference fields and if even one of the joined fields had a yes, show a Y, otherwise show a N - see below example
As I mentioned, all my tests have been unsuccessful I'm afraid, so I would appreciate any assistance that you can provide.
You can use the following:
;WITH selected as (
select min(ContactID) as ContactID, Mail, max(EmergencyContact) as EmergencyContact,
max(AccountsCon) as AccountsCon, max(WHSContact) as WHSContact
from t
GROUP BY Mail
)
select t.ContactID, t.BusinessID, t.BusinessName, t. FirstName, t.LastName, t.Position, t.Mail, s.EmergencyContact, s.AccountsCon, s.WHSContact
from selected as s
inner join t as t ON t.ContactID = s.ContactID
This way you get the contactid, businessid, businessname, firstname, lastname and position from the first record found with each email and the last 3 columns you get using max (taking advantage that Y is greater than N, so if there is at least one Y it will get Y).
I think you can just use aggregation:
select businessid, businessname, max(firstname),
max(lastname), max(position),
email,
max(emergencycontact),
max(accountscor),
max(whcontact)
from t
group by businessid, businessname, email;
I have two queries I need in one table, and haven't been able to find results in searching.
In the first table there is a UserID, which is a number, along with what the actual user id is and user's name.
My issue is that in every other query the user is only referred to as this number. I'm needing help in how to translate this UserID value into the actual User's name in my other queries.
Table with User's ID and User's Name:
SELECT *
FROM [Table].[dbo].[User]
Table example where the user is only referred to as this number, along with all other tables:
SELECT *
FROM [Table].[LoginStatus]
You need to join the two tables:
SELECT u.[UserName], l.*
FROM [LoginStatus] l
JOIN [Users] u ON u.id = l.user_id
I have a list of UserIds (which is a uniqueidentifier), Names, email addresses and relationships.
Something like
SELECT UserId, Name, Email, Relationship FROM Users
Sample data would look like:
F87B7702-F0EE-11D3-B288-0000B4A488D3 Peter peter#peter.com Member
ZZZZZZZZ-F0EE-11D3-B288-0000B4A488D2 Joan peter#peter.com Principal
AAAAAAAA-F0EE-11D3-EEEE-0000B4A488D3 Bob bob#bob.com Principal
Relationship can be either be 'Principal' or 'Member', but a principal user can also be a member.
An email address isn't specific to a user (often a member user will have the same email address as a principal user).
I need to ensure that I only select 1 user per email address so that the same person won't be emailed twice. If there are 2 emails for the same user I need to select the principal record.
What's the easiest way to do this, bearing in mind that you can't do a max on a uniqueidentifier field? For the sample data I gave above I would need to return only the second and third record.
I was leaning towards ordering by Relationship, doing a group by and then max but I don't think that's possible.
Output required is UserId, Name, Email.
The ORDER BY in ROW_NUMBER() will allow you to choose how to prioritise your emails. Such as how to deal with an email with no Principle but multiple Members (maybe add , Name ASC so the member with the first alphabetically ordered name gets chosen?)
SELECT
*
FROM
(
SELECT
*,
ROW_NUMBER() OVER (PARTITION BY email ORDER BY Relationship DESC) AS sequence_id
FROM
yourTable
)
AS sequenced_table
WHERE
sequence_id = 1
I didn't quite understood you, but if you want to get email only once, preffering the principle user this code will do:
select UserId, Name, Email, Relationship
from Table
where Relationship='Principle' or ( Relationship='Member' and Email not in
(
select Email
from Table
where Relationship='Principle'
)
)
This will give you the second and third lines. If there are more conditions- expand your example.
I have two tables, one stores the users, the other stores the users' email addresses.
table users: (userId, username, etc)
table userEmail: (emailId, userId, email)
I would like to do a query that allows me to fetch the latest email address along with the user record.
I'm basically looking for a query that says
FIRST ORDER BY userEmail.emailId DESC
THEN GROUP BY userEmail.userId
This can be done with:
SELECT
users.userId
, users.username
, (
SELECT
userEmail.email
FROM userEmail
WHERE userEmail.userId = users.userId
ORDER BY userEmail.emailId DESC
LIMIT 1
) AS email
FROM users
ORDER BY users.username;
But this does a subquery for every row and is very inefficient. (It is faster to do 2 separate queries and 'join' them together in my program logic).
The intuitive query to write for what I want would be:
SELECT
users.userId
, users.username
, userEmail.email
FROM users
LEFT JOIN userEmail USING(userId)
GROUP BY users.userId
ORDER BY
userEmail.emailId
, users.username;
But, this does not function as I would like. (The GROUP BY is performed before the sorting, so the ORDER BY userEmail.emailId has nothing to do).
So my question is:
Is it possible to write the first query without making use of the subqueries?
I've searched and read the other questions on stackoverflow, but none seems to answer the question about this query pattern.
But this does a subquery for every row and is very inefficient
Firstly, do you have a query plan / timings that demonstrate this? The way you've done it (with the subselect) is pretty much the 'intuitive' way to do it. Many DBMS (though I'm not sure about MySQL) have optimisations for this case, and will have a way to execute the query only once.
Alternatively, you should be able to create a subtable with ONLY (user id, latest email id) tuples and JOIN onto that:
SELECT
users.userId
, users.username
, userEmail.email
FROM users
INNER JOIN
(SELECT userId, MAX(emailId) AS latestEmailId
FROM userEmail GROUP BY userId)
AS latestEmails
ON (users.userId = latestEmails.userId)
INNER JOIN userEmail ON
(latestEmails.latestEmailId = userEmail.emailId)
ORDER BY users.username;
If this is a query you do often, I recommend optimizing your tables to handle this.
I suggest adding an emailId column to the users table. When a user changes their email address, or sets an older email address as the primary email address, update the user's row in the users table to indicate the current emailId
Once you modify your code to do this update, you can go back and update your older data to set emailId for all users.
Alternatively, you can add an email column to the users table, so you don't have to do a join to get a user's current email address.
I have a simple table with just name and email called name_email.
I am trying to fetch data out of it so that:
If two rows have the same name, but one has an email which is ending with ‘#yahoo.com’ and the other has a different email, then the one with the ‘#yahoo.com’ email should be discarded.
what would be best way to get this data out?
Okay, I'm not going to get involved in yet another fight with those who say I shouldn't advocate database schema changes (yes, you know who you are :-), but here's how I'd do it.
1/ If you absolutely cannot change the schema, I would solve it with code (either real honest-to-goodness procedural code outside the database or as a stored procedure in whatever language your DBMS permits).
This would check the database for a non-yahoo name and return it, if there. If not there, it would attempt to return the yahoo name. If neither are there, it would return an empty data set.
2/ If you can change the schema and you want an SQL query to do the work, here's how I'd do it. Create a separate column in your table called CLASS which is expected to be set to 0 for non-yahoo addresses and 1 for yahoo addresses.
Create insert/update triggers to examine each addition or change of a row, setting the CLASS based on the email address (what it ends in). This guarantees that CLASS will always be set correctly.
When you query your table, order it by name and class, and only select the first row. This will give you the email address in the following preference: non-yahoo, yahoo, empty dataset.
Something like:
select name, email
from tbl
where name = '[name]'
order by name, class
fetch first row only;
If your DBMS doesn't have an equivalent to the DB2 "fetch first row only" clause, you'll probably still need to write code to only process one record.
If you want to process all names but only the specific desired email for that name, a program such as this will suffice (my views on trying to use a relational algebra such as SQL in a procedural way are pretty brutal, so I won't inflict them on you here):
# Get entire table contents sorted in name/class order.
resultSet = execQuery "select name, email from tbl order by name, class"
# Ensure different on first row
lastName = resultSet.value["name"] + "X"
# Process every single row returned.
while not resultSet.endOfFile:
# Only process the first in each name group (lower classes are ignored).
if resultSet.value["name"] != lastName:
processRow resultSet.value["name"] resultSet.value["email"]
# Store the last name so we can detect next name group.
lastName = resultSet.value["name"]
select ne.*
from name_email ne
where ne.email not like '%#yahoo.com' escape '\' or
not exists(
select 1 from name_email
where name = ne.name and
email not like '%#yahoo.com' escape '\'
)
You could use something like the following to exclude invalid email addresses:
SELECT name, email
FROM name_email
WHERE email NOT LIKE '%#yahoo.com' // % symbol is a wildcard so joe#yahoo.com and guy#yahoo.com both match this query.
AND name = 'Joe Guy';
Or do it like this to include only the valid email address or domain:
SELECT name, email
FROM name_email
WHERE email LIKE '%#gmail.com'
AND name = 'Joe Guy';
This works well if you know ahead of time what specific names you are querying for and what email addresses or domains you want to exclude or include.
Or if you don't care which email address you return but only want to return one, you could use something like this:
SELECT DISTINCT (name, email)
FROM name_email;
You could do
SELECT TOP 1 email
FROM name_email
WHERE name = 'Joe Guy'
ORDER BY case when email like '%yahoo.com' then 1 else 0 end
So sort them by *#yahoo.com last and anything else first, and take the first one.
EDIT: sorry, misread the question - you want a list of each name, with only one email, and a preference for non-yahoo emails. Probably can use the above along with a group by, I'll have to rethink it.
Grabbing all the rows from the database, knowing not what the names are (and not needing to care about that really), but just want them to show, and if matching, skip a match if the email contains, in this case, #yahoo.com
SELECT DISTINCT name, email FROM name_email
WHERE email NOT LIKE '%#yahoo.com'
GROUP BY name;
Doing that will grab all the rows, but only one of a record if the names match with another row. But then, if there are two rows with matching names, junk the one with #yahoo.com in the email.
Not very pretty, but I believe it should work
select
ne.name
,ne.email
from
name_email ne
inner join (
select
name
,count(*) as emails_per_name
from
name_email
group by name
) nec
on ne.name = nec.name
where
nec.emails_per_name = 1
or (nec.emails_per_name > 1 and ne.email not like ('%#yahoo.com'))
That is assuming that the duplicate emails would be in yahoo.com domain - as specified in your question, and those would be excluded if there is more than one email per name
If you are working with SQL Server 2005 or Oracle, you can easily solve your problem with a ranking (analytical) function.
select a.name, a.name_email
from (select name, name_email,
row_number() over (partition by name
order by case
when name_email like '%#yahoo.com' then 1
when name_email like '%#gmail.com' then 1
when ... (other 'generic' email) then 1
else 0
end) as rn) as a
where a.rn = 1
By assigning different values to the various generic email names you can even have 'preferences'. As it is written here, if you have both a yahoo and a gmail address, you can't predict which one will be picked up.
You could use a UNION for this. Select everything without the yahoo.com and then just select the records that have yahoo.com and is not in the first list.
SELECT DISTINCT (name, name_email) FROM TABLE
WHERE name_email NOT '%yahoo.com'
UNION
SELECT DISTINCT (name, name_email) FROM TABLE
WHERE name NOT IN (SELECT DISTINCT (name, name_email) FROM TABLE
WHERE name_email NOT '%yahoo.com')