October 28, 2012 at 11:00 pm
Hi,
I am new to SQL. I have question regarding joins. Let us say i have 3 different tables
Table Workplace
Workplacecode (PK) autogenerated
WRegn
WorkplaceName
NumOfEmployees
EmpNumber (FK)
address_id(FK)
Table Employee
EmpNum (PK)
EmpName
Table Address
Address_id (PK)
address1
address2
phone1,
phone2
...
It is one to many relationship
Company can have many employees
Company can have one location address but can have multiple branch address.
I want to populate table workplace using joins. I tried to use below query, but i don get result of employee table and address table in Workplace table. Please let me know where am i missing
select Workplace.[WorkplaceCode], Workplace.WRegNum ,Workplace.[WorkplaceName],
Workplace.[NumOfEmployees],Employee.[EmpName] as EmpNum,address.[OfficePhNum],address.[HomePhone],
address.[Fax],address.[Address],address.[Address],address.homepage,address.[Email],Workplace.[Notes1],Workplace.[Notes2],Workplace.[Notes3],Workplace.[EmpNumber], Workplace.[AddressId] from Workplace
left join Employee on Workplace.[EmpNumber] = employee.EmpNum
left join Address on Workplace.[AddressId]=address.[Address_id]
October 28, 2012 at 11:15 pm
Hi,
i have doubt on table structure and design itself
in Workplace if its Primary key
then how can you put EmpNumber with it
each Employee have different Workplacecode ? if yes then what is NumOfEmployees in Workplace and address_id
if table fine according to you then please share some fake data so can give batter result
as far as your query left join seems ok.
October 28, 2012 at 11:40 pm
Hi,
Thanks for your response.
Workplacecode is autogenerated field and is primary key of Workplace table.
EmpNumber is FK to Workplace (It is the individual emp number)
NumOfEmployees is (count of employees in company)
Fake data
Workplace code-1
WRegNum-098-098 (Company reg Number)
WorkplaceName- Oracle Inc
NumOfEmplouees-1000
EmpName - 'John' (I get emp name from Employee table using EmpNumber which is FK to workplace table and using this only to get emp name)
[address -x-102,abc, Newyork
email -x@yz.com
Ph: 01-87483284] (I get address details from Address table and address_id is FK to Workplace table using this only to get address details of company)
October 28, 2012 at 11:50 pm
Okk now
for 2nd Employee it would be
Workplace code-2
WRegNum-098-098 (Company reg Number) (It will be same )
WorkplaceName- Oracle Inc
NumOfEmplouees-1000
EmpName - 'Bill' (I get emp name from Employee table using EmpNumber which is FK to workplace table and using this only to get emp name)
[address -x-102,abc, Newyork
email -x@yz.com
Ph: 01-87483284] (I get address details from Address table and address_id is FK to Workplace table using this only to get address details of company)
So Workplace code is changing with each and every employee also address and everything
is what you are saying?
October 28, 2012 at 11:59 pm
Is it what you want or just give me result which you want base on this data
so that can give you query
declare @workplace table(
Workplacecode int identity(1,1),
WRegn varchar(50),
WorkplaceName varchar(50),
NumOfEmployees int,
EmpNumber int,
address_id int
)
declare @Employee table(
EmpNumber int identity(1,1),
EmpName varchar(50)
)
declare @Address table(
Address_id int identity(1,1),
address1 varchar(50)
)
insert into @workplace values
('Test','Name',1000,1,1)
,('Test1','Name1',1000,2,1)
,('Test2','Name2',1000,3,3)
insert into @Employee values
('Empname'),
('Empname1'),
('Empname2')
insert into @Address values
('Add'),
('Add1'),
('Add2')
select * from @workplace as w
left join @Employee e on w.EmpNumber=e.EmpNumber
left join @Address a on w.address_id=a.Address_id
October 29, 2012 at 12:00 am
Workplace code is like row count as auto increment field. ( i guess i should not make this as primary key otherwise it will map each employee to one row right)
Instead i can make WRegn as PK for workplace where it can have 100 employees.
October 29, 2012 at 12:10 am
WorkplaceCodeWRegNumWorkplaceNameNumOfEmployeesEmpNameOfficePhNumAddressAddress_1Email
105 099-1A Oracle 888 Wang ho 201543115 Hyundai-4-ga Hyundai-4-ga x@hdfc.com
Above is the output when i run below query
select distinct Workplace.[WorkplaceCode], Workplace.WRegNum ,Workplace.[WorkplaceName], Workplace.[NumOfEmployees],Employee.[EmpName],address.[OfficePhNum],address.[HomePhone], address.[Fax],address.[Address],address.[Address],address.homepage,address.[Email],Workplace.[Notes1],Workplace.[Notes2],Workplace.[Notes3] from Workplace
left join Employee on Workplace.[EmpNumber] = employee.EmpNum
left join Address on Workplace.[AddressId]=address.[Address_id]
Also can you tell me if it is possible to disable Autoincrement field, i am using SQLite DB
October 29, 2012 at 12:37 am
yes create one more table
1)WRegn Master where WRegnNum is PK having(WRegnNum PK,Wregname,Address_id,NumOfEmployees)
2)Workplace (Workplacecode PK,WRegnNum,Empid)
3)EmployeeMaster
4)AddressMaster
so Data will not repeat and save your size and everything
now as far as join concern
still i am not getting what you want
you want all WRegn having employee or not having (use Left Join)
you want all WRegn having employee (use Inner join)
you want all employee having region or not(Use right join)
October 29, 2012 at 12:48 am
Thanks once again for you help. So i have to Normalize.
Basically I am looking for company having all the details of employee working in tat company( i guess your 2nd point "you want all WRegn having employee (use Inner join)")
as said this will include company details like registration number, address, number of employees and employee details.
The main purpose of this query is to display in GUI table
October 29, 2012 at 12:55 am
yes then go for Inner join and yes do Normalize you table ,
Like companymaster,workregmaster,empmaster,addressmaster,workdetail
just take care that data should not repeat in table ,it will affect size and performance.
you will get all you want using inner join.
October 29, 2012 at 1:01 am
Thank you very much for your help. I will follow as you said.
Also i have one question, is it possible to disable AUTOINCREMENT field? I am using SQLite DB
October 29, 2012 at 1:13 am
I havent try that Sqllite db
but if toy create table like
CREATE TABLE test (ID INTEGER PRIMARY KEY AUTOINCREMENT,Othercol varchar(20))
then try to remove AUTOINCREMENT from that and create table
October 29, 2012 at 1:15 am
Thanks for your help. 🙂
Also, i have one question, how to insert FK using insert query
Suppose i have table A containing FK
table A
Id_a
b
c
id_m (FK)
Now i want to do insert operation
insert into A( id_a,b,c,id_m) values (1,2,3,(select id_m from B where id_m=5))
Will above insert query work
October 29, 2012 at 1:17 am
SQLite doesnot allow to disable autoincrement field,so i thought if there is any way using SQL command.
October 29, 2012 at 1:27 am
insert into A( id_a,b,c,id_m) values (1,2,3,(select id_m from B where id_m=5))
This will work unless and until
select id_m from B where id_m=5 return only one(return multiple value not allowed gives error) value
and for autoincreament in SQLLITE DB i also need to do google.
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