How can I join 2 tables? - join

I would like to join tables . Could you please help?
Select Number, OwnerId from DNIS.numbers
select ID,Name from DNIS.owners
Thank you.

Normally, SQL servers allow you to join tables from different databases as long as the former all belong to them. Here is an example showing you how to do this (all you have to do is to explicitly write the database names associated to each table in the query):
SELECT N.Number, N.OwnerId, O.ID, O.Name
FROM DB1.[dbo].DNIS numbers N
JOIN DB2.[dbo].DNIS owners O ON O.ID = N.OwnerId
You can also use the following syntax:
SELECT N.Number, N.OwnerId, O.ID, O.Name
FROM DB1..DNIS numbers N
JOIN DB2..DNIS owners O ON O.ID = N.OwnerId

In order to accomplish that you will have to specify the table and column names in your join statement, like so:
SELECT db1.tablename.column, db2.tablename.column
FROM db1.tablename INNER JOIN db2.tablename
ON db1.tablename.id = db2.tablename.id;

Related

LEFT JOIN using _PARTITIONDATE

I'm currently using StandardSQL in BigQuery, I tried to join two sets of table one of which is a pseudo-column table partitioned by day.
I tried to use this query below:
SELECT
DISTINCT DATE(create_time) AS date,
user_id,
city_name,
transaction_id,
price
FROM
table_1 a
LEFT JOIN (SELECT user_id, city_name FROM table_2) b
ON (a.user_id = b.user_id AND DATE(create_time) = _PARTITIONDATE)
I've tried this kind of JOIN (using _PARTITIONDATE) and worked out, but for this particular query I got an error message:
Unrecognized name: _PARTITIONDATE
Can anyone tell me why this happened, and how could I solve this? Thanks in advance.
The issue is that you are not selecting the _PARTITIONDATE field from table_2 when joining it so it can't recognize it:
SELECT user_id, city_name FROM table_2
In order to solve it you can add it as follows:
SELECT
DISTINCT DATE(create_time) AS date,
user_id,
city_name,
transaction_id,
price
FROM
table_1 a
LEFT JOIN (SELECT _PARTITIONDATE AS pd, user_id, city_name FROM table_2) b
ON (a.user_id = b.user_id AND DATE(create_time) = pd)
Note that you'll need an alias such as pd as it's a pseudocolumn
Probably it was working in the past if you were joining two tables directly such as in (you don't get selectivity benefits in that case):
FROM
table_1 a
LEFT JOIN table_2 b
ON (a.user_id = b.user_id AND DATE(create_time) = _PARTITIONDATE)

SQL placement join with student, friend, package

Issue:
You are given three tables: Students, Friends and Packages.
Students contains two columns: ID and Name.
Friends contains two columns: ID and Friend_ID (ID of the ONLY best friend).
Packages contains two columns: ID and Salary (offered salary in $ thousands per month).
Write a query to output the names of those students whose best friends got offered a higher salary than them. Names must be ordered by the salary amount offered to the best friends. It is guaranteed that no two students got same salary offer.
Code:
This is the code that I have come up with but it does not produce correct results. Can anyone let me know why?
select TableA.name
from
(select s.id,s.name,p.salary from students s inner join packages p on s.id=p.id) TableA,
(select f.id,f.friend_id, p2.salary from friends f inner join packages p2 on f.friend_id=p2.id) TableB
where TableA.id=TableB.id And TableA.salary>TableB.salary
order by TableB.salary desc;
I think in your query you wrote AND TableA.salary < TableB.salary instead of AND TableA.salary > TableB.salary.
Moreover I think your query can be written in a more synthetic way.
On MSSQL (but it works on MYSQL too, as query is very basic), you can try to use this one:
SELECT s.id
,s.NAME
,p.salary
, f.friend_id, p2.salary as friend_salary
FROM students s
INNER JOIN packages p ON s.id = p.id
LEFT JOIN friends f ON f.id = s.id
LEFT JOIN packages p2 ON f.friend_id = p2.id
WHERE p.salary <= p2.salary
ORDER BY s.id;
Output:
id NAME salary friend_id friend_salary
1 John 1000 2 1200
3 Pete 800 1 1000
Sample data:
CREATE TABLE students (id int, NAME VARCHAR(30));
CREATE TABLE packages (id int, salary INT);
CREATE TABLE friends (id int, friend_id INT);
INSERT INTO students values (1,'John');
INSERT INTO students values (2,'Arthur');
INSERT INTO students values (3,'Pete');
INSERT INTO packages values (1,1000);
INSERT INTO packages values (2,1200);
INSERT INTO packages values (3,800);
INSERT INTO friends values (1,2);
INSERT INTO friends values (2,3);
INSERT INTO friends values (3,1);
I used CTE for easy code readability. I am not sure whether it is fully optimized or not. But, it yields the result as expected from the question.
with std_salary as (
SELECT s.id, s.name, p.salary
FROM Students s
JOIN Packages p
ON s.id=p.id),
friend_salary as (
SELECT f.id, p.salary
FROM Friends f
JOIN Packages p
ON f.friend_id=p.id
)
SELECT name
FROM
(SELECT std_salary.name, std_salary.salary as own, friend_salary.salary as friend
FROM std_salary
JOIN friend_salary
ON std_salary.id=friend_salary.id) as final
WHERE final.own<final.friend
ORDER BY final.friend;
This worked for me in MS SQL
SELECT a.name
FROM (SELECT students.id as main_id, students.name, packages.salary
FROM students join packages on students.id = packages.id) a
JOIN (SELECT f.id as main_id1, p.salary
FROM friends f JOIN packages p ON f.friend_id = p.id) b
ON a.main_id = b.main_id1
WHERE b.salary>a.salary
ORDER BY b.salary ASC;
you have written 'where TableA.salary>TableB.salary' implying that you want to find rows where your salary is > than your friends. But the question asked was the opposite (to find names where the firends salary is > than your salary) so you can change that to 'where TableB.salary>TableA.salary' and it should work.
select my_name from
(select s.id as my_id,s.name my_name,p.salary as my_salary from students s
inner join packages p on s.id=p.id) as my_tbl inner join (select f.id as
id,f.friend_id as frnd_id,p.salary as frnd_salary from friends f inner join
packages p on f.friend_id=p.id ) as frnd_tbl on my_id=id where
frnd_salary>my_salary order by frnd_salary;

Optimizing SQL query using JOIN instead of NOT IN

I have a sql query that I'd like to optimize. I'm not the designer of the database, so I have no way of altering structure, indexes or stored procedures.
I have a table that consists of invoices (called faktura) and each invoice has a unique invoice id. If we have to cancel the invoice a secondary invoice is created in the same table but with a field ("modpartfakturaid") referring to the original invoice id.
Example of faktura table:
invoice 1: Id=152549, modpartfakturaid=null
invoice 2: Id=152592, modpartfakturaid=152549
We also have a table called "BHLFORLINIE" which consists of services rendered to the customer. Some of the services have already been invoiced and match a record in the invoice (FAKTURA) table.
What I'd like to do is get a list of all services that either does not have an invoice yet or does not have an invoice that's been cancelled.
What I'm doing now is this:
`SELECT
dbo.BHLFORLINIE.LeveringsDato AS treatmentDate,
dbo.PatientView.Navn AS patientName,
dbo.PatientView.CPRNR AS patientCPR
FROM
dbo.BHLFORLINIE
INNER JOIN dbo.BHLFORLOEB
ON dbo.BHLFORLOEB.BhlForloebID = dbo.BHLFORLINIE.BhlForloebID
INNER JOIN dbo.PatientView
ON dbo.PatientView.PersonID = dbo.BHLFORLOEB.PersonID
INNER JOIN dbo.HENVISNING
ON dbo.HENVISNING.BhlForloebID = dbo.BHLFORLOEB.BhlForloebID
LEFT JOIN dbo.FAKTURA
ON dbo.BHLFORLINIE.FakturaId = FAKTURA.FakturaId
WHERE
(dbo.BHLFORLINIE.LeveringsDato >= '2017-01-01' OR dbo.BHLFORLINIE.FakturaId IS NULL) AND
dbo.BHLFORLINIE.ProduktNr IN (110,111,112,113,8050,4001,4002,4003,4004,4005,4006,4007,4008,4009,6001,6002,6003,6004,6005,6006,6007,6008,7001,7002,7003,7004,7005,7006,7007,7008) AND
((dbo.FAKTURA.FakturaType = 0 AND
dbo.FAKTURA.FakturaID NOT IN (
SELECT FAKTURA.ModpartFakturaID FROM FAKTURA WHERE FAKTURA.ModpartFakturaID IS NOT NULL
)) OR
dbo.FAKTURA.FakturaType IS NULL)
GROUP BY
dbo.PatientView.CPRNR,
dbo.PatientView.Navn,
dbo.BHLFORLINIE.LeveringsDato`
Is there a smarter way of doing this? Right now the added the query performs three times slower because of the "not in" subquery.
Any help is much appreciated!
Peter
You can use an outer join and check for null values to find non matches
SELECT customer.name, invoice.id
FROM invoices i
INNER JOIN customer ON i.customerId = customer.customerId
LEFT OUTER JOIN invoices i2 ON i.invoiceId = i2.cancelInvoiceId
WHERE i2.invoiceId IS NULL

Unusual Joins SQL

I am having to convert code written by a former employee to work in a new database. In doing so I came across some joins I have never seen and do not fully understand how they work or if there is a need for them to be done in this fashion.
The joins look like this:
From Table A
Join(Table B
Join Table C
on B.Field1 = C.Field1)
On A.Field1 = B.Field1
Does this code function differently from something like this:
From Table A
Join Table B
On A.Field1 = B.Field1
Join Table C
On B.Field1 = C.Field1
If there is a difference please explain the purpose of the first set of code.
All of this is done in SQL Server 2012. Thanks in advance for any help you can provide.
I could create a temp table and then join that. But why use up the cycles\RAM on additional storage and indexes if I can just do it on the fly?
I ran across this scenario today in SSRS - a user wanted to see all the Individuals granted access through an AD group. The user was using a cursor and some temp tables to get the users out of AD and then joining the user to each SSRS object (Folders, reports, linked reports) associated with the AD group. I simplified the whole thing with Cross Apply and a sub query.
GroupMembers table
GroupName
UserID
UserName
AccountType
AccountTypeDesc
SSRSOjbects_Permissions table
Path
PathType
RoleName
RoleDesc
Name (AD group name)
The query needs to return each individual in an AD group associated with each report. Basically a Cartesian product of users to reports within a subset of data. The easiest way to do this looks like this:
select
G.GroupName, G.UserID, G.Name, G.AccountType, G.AccountTypeDesc,
[Path], PathType, RoleName, RoleDesc
from
GroupMembers G
cross apply
(select
[Path], PathType, RoleName, RoleDesc
from
SSRSOjbects_Permissions
where
Name = G.GroupName) S;
You could achieve this with a temp table and some outer joins, but why waste system resources?
I saw this kind of joins - it's MS Access style for handling multi-table joins. In MS Access you need to nest each subsequent join statement into its level brackets. So, for example this T-SQL join:
SELECT a.columna, b.columnb, c.columnc
FROM tablea AS a
LEFT JOIN tableb AS b ON a.id = b.id
LEFT JOIN tablec AS c ON a.id = c.id
you should convert to this:
SELECT a.columna, b.columnb, c.columnc
FROM ((tablea AS a) LEFT JOIN tableb AS b ON a.id = b.id) LEFT JOIN tablec AS c ON a.id = c.id
So, yes, I believe you are right in your assumption

joins on multiple related tables

I have 3 table customer (customerid,name), customerbooking(bookingid,customerid), transact(transacted,bookingid,typeoftransaction)
I want to fetch the name of the ‘customer name’ who has the maximum typeoftransact=’current’. Customer table is linked to customerbooking via customerid, and customerbooking is linked to transact via bookingid. Using join I am able to get the individual records, but unable to get the Max value
Please try this to meet your scenerio
SELECT
C.Name
, Count(BookingID)
FROM Customer C
INNER JOIN customerbooking CB ON CB.CustomerID = C.customerId
INNER JOIN transact T ON T.bookingid = CB.BookingId
WHERE T.Typeoftransaction='current'
GROUP BY C.Name
Hope this helps

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