Greetings fellow Earthlings,
I have a problem. Let me start by laying out my table structure:
CREATE TABLE Person
(
id varchar(50) NOT NULL PRIMARY KEY,
name varchar(50) NOT NULL,
adress varchar(50) NOT NULL references Adress(id)
)
CREATE TABLE Adress
(
id varchar(50) NOT NULL PRIMARY KEY,
addressName varchar(50),
city varchar(50),
aState varchar(50),
linkToCountry varchar(50) references Country(id)
)
CREATE TABLE Country
(
id varchar(50) NOT NULL PRIMARY KEY,
countryName varchar(50)
)
What I want to achieve is: select a person 'name' along with their 'addressName' and the 'countryName' they're from.
I know that this is a joining related issue but I can't seem to figure this one out.
So any help from people who are well versed on SQL?
Would appreciate it very very much any one has links to advance sql joining so I can familiarize myself with it.
You can get the result using simple join as below. This will retrun the person name with address name, and country name. However it returns only those person names which has an address record in the address table and country record in the country table. If you want to retrieve all the persons irrespective of whether address/country exists or not, you need to use left join.
SELECT Person.Name, Address.addressname,Country.countryName
FROM Person
JOIN Address on Person.address = Address.Id
JOIN Country ON Address.linkToCountry = Country.id
Try this:
SELECT p.name, a.addressName, c.countryName
FROM Person p
INNER JOIN Adress a ON p.adress = a.id
LEFT OUTER JOIN Country c ON a.linkToCountry = c.id
Related
I am working on Bus route management system , I made two table first one is Cities and second one is route have following queries
CREATE TABLE Cities
(
ID NUMBER GENERATED ALWAYS AS IDENTITY(START with 1 INCREMENT by 1) PRIMARY KEY,
Name Varchar(30) not null,
)
CREATE TABLE route
(
ID NUMBER GENERATED ALWAYS AS IDENTITY(START with 1 INCREMENT by 1) PRIMARY KEY,
Name Varchar(30) not null,
from NUMBER not null,
to NUMBER NOT NULL,
CONSTRAINT FROM_id_FK FOREIGN KEY(from) REFERENCES Cities(ID),
CONSTRAINT TO_id_FK FOREIGN KEY(to) REFERENCES Cities(ID),
)
i am joining the table through inner join
select CITIES.Name
from CITIES
inner join ROUTES on CITIES.ID=ROUTES.ID
but it show single column as
Name
-----------
but i want result as
from | to
------------------------
what is possible way to do this using inner join
I suspect you need something like the following:
select r.Name, cs.Name SourceCity, cd.Name DestinationCity
from routes r
join cities cs on cs.id = r.from
join cities cd on cd.id = r.to
Hope is working for you
select CITIES.Name,ROUTES.from,ROUTES.to
from CITIES inner join ROUTES on CITIES.ID=ROUTES.ID
I need to select the item name and the vendor name for each item that belongs to the vendor with a rating bigger than 4. And I can't find a way, I know it's something with joins but the 2 of them have the same column name.
CREATE TABLE venedors(
id int PRIMARY KEY,
name varchar2(20),
rating int)
CREATE TABLE items(
id int PRIMARY KEY,
name varchar2(20),
venedorId int references venedors(id))
If i understanded your problem.
Select items.name as itemName, venedors.name as vendorName
from items
inner join venedors
on items.venedorId = venedors.id
where venedors.rating > 4
If you want get all the vendors irrespective whether there are items associated with vendors or not, then try with left join as shown below:
Select v.name as vendorName, i.name as itemName
from venedors v
left join items i
on i.venedorId = v.id
where v.rating > 4
I have the following tables in a SQL database:
t_customers
ID_operator int primary key auto_incr
firstname varchar(30)
lastname varchar(30)
email varchar(100)
t_operator
ID_operator int primary key auto_incr
firstname varchar(30)
lastname varchar(30)
course varchar(10)
I have another table, which represents an order, in which I join both fields when querying another field:
SELECT
*, // table t_orders
t_customers.firstname,
t_customers.lastname,
t_operator.firstname AS operator_firstname,
t_operator.lastname AS operator_lastname
FROM
t_orders
CROSS JOIN
t_customers, t_operator
WHERE
id_orders IS 1;
I have tried to alleviate this by using the AS keyword and the new fields do get added, but I still have 2 fields named "firstname" and "lastname" in my query, preventing me from working with it correctly. Is there any solution besides renaming the tables?
Are you trying to do something like this?
SELECT o.*, // table t_orders
c.firstname, c.lastname,
op.firstname AS operator_firstname,
op.lastname AS operator_lastname
FROM t_orders o JOIN
t_customers c
ON o.id_customer = c.id_customer JOIN
t_operator op
ON c.id_operator = c.id_operator
WHERE id_orders = 1;
I have 2 tabels
create table Students(
SerialNumber int primary key identity,
Name varchar(50) not null,
Surname varchar(50) not null,
AcademicProgram int foreign key references AcademicProgrammes(Id)
)
Create table AcademicProgrammes(
Id int primary key identity,
Name varchar (20) not null
)
and I want to get from students table all the students, but instead the AcademicProgram reference foreign key I want the name of the AcademicProgrammes.
my join looks like this :
select Students.SerialNumber,Students.Name, Students.Surname, AcademicProgrammes.Name
from Students left join
AcademicProgrammes on Students.SerialNumber=AcademicProgrammes.Id
if i have 2 academic programs master's and undergraduate
as a result I get all ste students but as the academic program name column only the first 2 students have the name of de academic program, and the rest of them have null
Vasile Magdalena-Maria Licenta
Ciotmonda Oana-Maria Master
Rus Diana NULL
Turcu Gabriel NULL
I can't find what I'm doing wrong
Thanks !
I believe you need to join by
Students.AcademicProgram=AcademicProgrammes.Id
instead of
Students.SerialNumber=AcademicProgrammes.Id
Because of that you're getting names of academic programs for only students with serial numbers 1 and 2 (since you have only two programs).
Therefore try following
SELECT s.SerialNumber,
s.Name,
s.Surname,
a.Name AS Program
FROM Students s LEFT JOIN
AcademicProgrammes a ON s.AcademicProgram=a.Id
I have one table Person:
Id Name
1 Person1
2 Person2
3 Person3
And I have its child table Profile:
Id PersonId FieldName Value
1 1 Firstname Alex
2 1 Lastname Balmer
3 1 Email some_email#test.com
4 1 Phone +1 2 30004000
And I want to get data from these two tables in one row like this:
Id Name Firstname Lastname Email Phone
1 Person1 Alex Balmer some_email#test.com +1 2 30004000
What is the most optimized query to get these vertical (key, value) values in one row like this? Now I have a problem that I done four joins of child table to parent table because I need to get these four fields. Some optimization is for sure possible.
I would like to be able to modify this query in easy way when I add new field (key,value). What is the best way to do this? To create some stored procedure?
I would like to have strongly types in my DB layer (C#) and using LINQ (when programming) so it means when I add some new Key, Value pair in Profile table I would like to do minimal modifications in DB and C# if possible. Actually I am trying to get some best practices in this case.
Select
P.ID
, P.Name
, Case When C.FieldName = 'FirstName' Then C.Value Else NULL END AS FirstName
, Case When C.FieldName = 'LastName' Then C.Value Else NULL END AS LastName
, Case When C.FieldName = 'Email' Then C.Value Else NULL END AS Email
, Case When C.FieldName = 'Phone' Then C.Value Else NULL END AS Phone
From Person AS P
Inner JOIN Child AS C
ON P.ID = C.PersonID
You could use PIVOT; not sure which one would be the easiest for you to add a new column.
best optimized way with strongly typed fields, is to do it this way:
CREATE TABLE Persons
(PersonID int identity(1,1) primary key
,Firstname varchar(...)
,Lastname varchar(...)
,Email varchar(...)
,Phone varchar(...)
,....
)
then the most optimized query would be:
SELECT
PersonID,Firstname,Lastname,Email,Phone
FROM Persons
WHERE ...
Add all main columns into the persons table. if you need to specialize create additional tables:
--one person can play many instruments with this table
CREATE TABLE PersonMusicians
(PersonID int --pk fk to Persons.PersonID
,InstrumentCode char(1) --pk
,...
)
--only one row per person with this table
CREATE TABLE PersonTeachers
(PersonID int --pk fk to Persons.PersonID
,FavoriteSubjectCode char(1)
,SchoolName varchar(...)
)
if you have to have unlimited dynamic attribute fields, then I would create the above structure as fully as possible (as many common fields as possible) and then have an "AdditionalInfo" table where you store all the info like:
AdditionalInfoFields
FieldID int identity(1,1) primary key
FieldName varchar(...)
AdditionalInfo
AdditionalInfoID int identity(1,1) primary key
PersonID int fk to Persons.PersonID
FieldID int fk to AdditionalInfoFields.FieldID
FieldValue varchar(..) or you can look into sql_variant
have an index on AdditionalInfo.PersonID+FieldID and if you will search for all people that have attribute X, then also another like AdditionalInfo.FieldID+PersonID
short of any of the above, you will need to use the four left outer joins like you have mentioned in your option #1:
SELECT
P.ID, p.Name
, p1.Value AS Firstname
, p2.value AS Lastname
, p3.Value AS Email
, p4.Value AS Phone
FROM Persons p
LEFT OUTER JOIN Profile p1 ON p.PersonID=p1.PersonID AND p1.FieldName='Firstname'
LEFT OUTER JOIN Profile p1 ON p.PersonID=p1.PersonID AND p1.FieldName='Lastname'
LEFT OUTER JOIN Profile p1 ON p.PersonID=p1.PersonID AND p1.FieldName='Email'
LEFT OUTER JOIN Profile p1 ON p.PersonID=p1.PersonID AND p1.FieldName='Phone'
WHERE ....
you could always make a materialized view with an index out of this 4 left join query and have the data precalculated for you which should speed it up.