I have been trying to join two tables (USERS AND USERS_ROLES) based on their role id I put the left join on following query
users.id = users_roles.fk_user_id
but the output is not correct of users_roles.fk_role_id coulmun and shows NULL where it should display the id of users.id = users_roles.fk_user_id that is 4 (at most places) because on users.id = users_roles.fk_user_id the value of users_roles.fk_role_id = 4
Kindly let me know how can i fix that so my query should result the exact vlaues of ids where they match,
Thanks
SELECT users.id, users.v_first_name, users.v_last_name, user_facility.fk_facility_id,users.fk_tenant_id, marital_status.v_marital_status,
users.v_blood_type, NOW(),users_roles.fk_role_id
FROM users
LEFT JOIN (user_facility, marital_status, users_roles) ON
users.id = user_facility.fk_user_id AND users.fk_marital_status_id=marital_status.id AND users.id = users_roles.fk_user_id
Usage of AND operator when used with Left or Right join gives different result. You should be clear what you are trying to accomplish..See this
well it is what you get by first implicitly inner-joining 3 tables and then explicitly left-joining the result to a 4th table only if 3 conditions relevant to all of the 3 inner-joinded tables are matched (i.e. when 3rd condition is false, nothing is joined from either of the 2 remaining tables)
i strongly suggest not to combine implicit and explicit joins, i personally use explicit joins all the time:
if you need an outer join:
SELECT ...
FROM users
LEFT JOIN user_facility ON users.id = user_facility.fk_user_id
LEFT JOIN marital_status ON users.fk_marital_status_id=marital_status.id
LEFT JOIN users_roles ON users.id = users_roles.fk_user_id
if you need an inner join:
SELECT ...
FROM users
JOIN user_facility ON users.id = user_facility.fk_user_id
JOIN marital_status ON users.fk_marital_status_id=marital_status.id
JOIN users_roles ON users.id = users_roles.fk_user_id
or if you prefere implicit inner joins for some obscure reason:
SELECT ...
FROM users,
user_facility,
marital_status,
users_roles
WHERE users.id = user_facility.fk_user_id
AND users.fk_marital_status_id=marital_status.id
AND users.id = users_roles.fk_user_id
(implicit outer joins are getting deprecated in all RDBMS as far as i know)
When it shows NULL it means there isn't a correspondency (relation) between all tables in the JOIN clause.
If you want to show only the ones that have relations in all tables, use INNER JOIN instead.
SELECT u.id,
u.v_first_name,
u.v_last_name,
uf.fk_facility_id,
u.fk_tenant_id,
ms.v_marital_status,
u.v_blood_type,
NOW(),
ur.fk_role_id
FROM users u
INNER JOIN user_facility uf ON u.id = uf.fk_user_id
INNER JOIN marital_status ms ON u.fk_marital_status_id=ms.id
INNER JOIN users_roles ur ON u.id = ur.fk_user_id
Related
I am stuck with some SQL query.
I have four tables. Which are connected:
user =>user_account=>acount_profile_entries=>profile_entries
From left to right they are one to many.
user_account has a user_id field as FK.
account_profile_field has user_account_id and profile_entry_id.
Profile_entries has a text field that I need to show for each user (account).
I need to write a query that will show me, all accounts for every user, and its profile entries.
I am sorry if this is confusing, I tried to make it simple
This is what I have done so far. I can show all accounts for every user and this is the point I am stuck with. Last two commented out Joins are not working properly. I believe I am close somewhat, I just need a push :)
SELECT
u.email AS Email,
u.id AS UserId,
ua.id AS UserAccountId,
ua.app_id AS Application
FROM users AS u
INNER JOIN user_accounts ua ON ua.user_id = u.id
-- INNER JOIN account_profile_entries ape ON ape.user_account_id = ua.id
-- INNER JOIN profile_entries as pe ON pe.id = ape.profile_entry_id
limit 10
Try this SQL Query with using LEFT JOIN
Description :- The MySQL LEFT JOIN joins two tables and fetches rows based on a condition, which is matching in both the tables and the unmatched rows will also be available from the table written before the JOIN clause.
SYNTAX
SELECT column_name(s)
FROM table1
LEFT JOIN table2 ON table1.column_name = table2.column_name;
SELECT u.*,
u.id AS UserId,
ua.id AS UserAccountId,
ua.app_id AS Application,pe.* FROM `users` u
LEFT JOIN user_accounts ua ON ua.user_id = u.id
LEFT JOIN account_profile_entries ape ON ape.user_account_id = ua.id
LEFT JOIN profile_entries as pe ON pe.id = ape.profile_entry_id LIMIT 10
My query looks like:
SELECT *
FROM users U
LEFT JOIN posts P ON P.userId = U.id AND P.userId IS NOT NULL;
Why the query also return result where userId is null ?
I know that for my needs I can use INNER JOIN to get only posts related to user but is so strange that LEFT JOIN support multiple conditions, but not work with NOT NULL conditions.
This is because "posts" does not contain the null-values and hence they can´t be filtered at that stage. The Null-values are only generated trough the join, when the server can´t find a corresponding row on the right table. So just put the not null in the where clause and it will work:
SELECT * FROM users U LEFT JOIN posts P ON P.userId = U.id WHERE userId IS NOT NULL;
(EDIT: You should use an inner join for productive work though, as it is the proper way and will give you much greater performance.)
You can also see all users who don´t have posts by inverting that:
SELECT * FROM users U LEFT JOIN posts P ON P.userId = U.id WHERE userId IS NULL;
You are outer joining the posts table. This means for every users record that has no match in posts you still get this record with all posts columns null.
So say you have a users record with userid = 5 and there is no posts record with id = 5.
ON P.userId = U.id AND P.userId IS NOT NULL
The two combined conditions are not met (there is no record with userid 5), so you get the users record with all posts columns set to null in your results.
Maybe you are simply looking for an inner join? All users records with their posts data?
This query:
SELECT *
FROM users U LEFT JOIN
posts P
ON P.userId = U.id AND P.userId IS NOT NULL;
Returns all rows in the users as well as all columns from posts, regardless of whether or not they match. This is true, regardless of whether the ON clause evaluates to TRUE or FALSE.
What you want is a WHERE. In addition, you should only select the columns from users:
SELECT u.*
FROM users U LEFT JOIN
posts P
ON P.userId = U.id
WHERE P.userId IS NOT NULL;
Note that you can also accomplish this using NOT IN or NOT EXISTS.
Because the LEFT JOIN must return every row from the left table by it's definition. The raw may be augmented with the data of the right table depending on the ON clause evaluation. So the following code must return a row.
select u.*, p.*
from (
select 1 as id
) u
left join (
-- no data at all
select 2 as id where 1=2
) p on 3 = 4 -- never is true
Try this
SELECT * FROM users U LEFT JOIN posts P ON P.userId = U.id
SELECT * FROM users U LEFT JOIN posts P ON P.userId = U.id where P.userId IS NOT NULL;
IS NOT NULL WITH JOINS
SELECT * FROM users
LEFT JOIN posts ON post.user_id = users.id
WHERE user_id IS NOT NULL;
the MYSQL query below combines a number of tables. However, as you can see, I would like to add a LEFT JOIN at the end on the receipt table. The query returns an error when I add the LEFT JOIN. Anybody know the best way to LEFT JOIN the receipt table to the rest of the query. Sorry if this is a newbie question. Thanks !!
SELECT user_name, expense_category, merchant_name, expense_cost, expense_date, expense_status, receipt_image, expense_comment
FROM users, expenses, merchants, receipts
WHERE ".$adminId." = expenses.admin_id
AND expenses.user_id = users.user_id
AND expenses.merchant_id = merchants.merchant_id
AND LEFT JOIN (receipts)
ON expenses.receipt_id = receipts.receipt_id
Here is a clean approach of doing it, note that I have added alias for the tables for better readability so you may use the alias name in the select statement to fetch the column from the proper table.
SELECT
u.user_name,
ex.expense_category,
mer.merchant_name,
ex.expense_cost,
ex.expense_date,
ex.expense_status,
re.receipt_image,
ex.expense_comment
FROM users u
JOIN expenses ex on ex.user_id = u.user_id
JOIN merchants mer on mer.merchant_id = ex.merchant_id
LEFT JOIN receipts re on re.receipt_id = ex.receipt_id
where
ex.admin_id = '$adminId'
Try this,
SELECT user_name, expense_category, merchant_name, expense_cost, expense_date, expense_status, receipt_image, expense_comment
FROM users, expenses, merchants, receipts
LEFT JOIN receipts ON expenses.receipt_id = receipts.receipt_id
WHERE ".$adminId." = expenses.admin_id
AND expenses.user_id = users.user_id
AND expenses.merchant_id = merchants.merchant_id
Use join clauses instead of where clause. I.e.
SELECT user_name, expense_category, merchant_name, expense_cost, expense_date, expense_status, receipt_image, expense_comment
FROM users
INNER JOIN expenses on users.user_id = expenses.expenses_id
INNER JOIN merchants on merchants.merchant_id = expenses.merchant_id
LEFT JOIN (receipts)
ON expenses.receipt_id = receipts.receipt_id
WHERE ".$adminId." = expenses.admin_id
Note that any columns from the receipts will be NULL in the select statement whenever there's no matching record.
I'm trying to get MySQL to return me all instructors who don't have a booking at a certain time. This query is essentially the search query. So return all instructors and their details that aren't already booked basically. Could someone help me finish it off?
SELECT
AddressTypes.AddressTypeName,
Addresses.*,
InstructorSettings.*,
Users.*,
BookedSlots.DateTime
FROM Users
LEFT OUTER JOIN InstructorSettings
ON Users.UserID = InstructorSettings.UserID
LEFT OUTER JOIN Addresses
ON Users.UserID = Addresses.UserID
INNER JOIN AddressTypes
ON Addresses.AddressTypeID = AddressTypes.AddressTypeID
LEFT OUTER JOIN BookedSlots
ON Users.UserID = BookedSlots.UserID
WHERE Users.AccountTYpe = 3 AND Addresses.PostCode1 IN ('l13') AND BookedSlots.DateTime <> '2013-04-25 11:00:00'
The query above doesn't return anything, but if I take out the "AND BookedSlots.DateTime <> '2013-04-25 11:00:00'" it returns all the instructors details fine.
Database
It looks to me as if what you're looking for is the lack of existence of records in BookedSlots for the specified time.
I'm not sure if this is considered MySQL best practices, but I typically accomplish that task not with a join, but with a sub-select or a temp table, like so:
SELECT
AddressTypes.AddressTypeName,
Addresses.*,
InstructorSettings.*,
Users.*,
FROM Users
LEFT OUTER JOIN InstructorSettings
ON Users.UserID = InstructorSettings.UserID
LEFT OUTER JOIN Addresses
ON Users.UserID = Addresses.UserID
INNER JOIN AddressTypes
ON Addresses.AddressTypeID = AddressTypes.AddressTypeID
WHERE Users.AccountType = 3 AND Addresses.PostCode1 IN ('l13')
AND Users.UserID not in (SELECT BookedSlots.InstructorID FROM BookedSlots
WHERE BookedSlots.DateTime = '2013-04-25 11:00:00')
EDIT: per comments, changed the select statement to disclude BookedSlots, and the sub-select to return InstructorId (which matches instructors instead of students on the booking).
To check that there aren't any bookings on a particular timeslot, include the timeslot in the join conditions and select where the timeslot id is null - like so:
SELECT
AddressTypes.AddressTypeName,
Addresses.*,
InstructorSettings.*,
Users.*,
BookedSlots.DateTime
FROM Users
LEFT OUTER JOIN InstructorSettings
ON Users.UserID = InstructorSettings.UserID
LEFT OUTER JOIN Addresses
ON Users.UserID = Addresses.UserID
INNER JOIN AddressTypes
ON Addresses.AddressTypeID = AddressTypes.AddressTypeID
LEFT OUTER JOIN BookedSlots
ON Users.UserID = BookedSlots.UserID AND
BookedSlots.DateTime = '2013-04-25 11:00:00'
WHERE Users.AccountTYpe = 3 AND
Addresses.PostCode1 IN ('l13') AND
BookedSlots.UserID is null
Suppose we have this model:
As you see industry_id can be null. Can I fetch industry.name (if any), user.description, profile.name and project.title (all project titles) he/she has with a single MySQL query while having user.id?
Yes, JOIN the two tables:
SELECT
i.name,
u.id
FROM Industry AS i
LEFT JOIN `User` AS u ON u.industry_id = i.industry_id;
Update:
For multiple tables:
SELECT
i.Name AS InustryName,
p.Name AS UserName,
u.Description,
j.title AS ProjectTitle
FROM Industry AS i
INNER JOIN User AS u ON i.id = u.id
INNER JOIN Profile AS p ON p.user_id = u.id
INNER JOIN Project AS j ON u.id = j.user_id;
Note that: I used INNER JOIN between the tables, this will give you only the matched rows from the joined tables, you might need to use LEFT JOIN instead of innner join to include the untmatched rows, i.e., to get those industries that has no entries in the other tables. See this blog post:
A Visual Explanation of SQL Joins