I work on a program VB.Net using a SQL Server Compact database.
I want to create a table PRODUCTION where I can have many employees so I want to create a column as collection of names of employees:
This is the table Employee :
CREATE TABLE [Employee]
(
[ID] INT NOT NULL IDENTITY (1,1),
[nom] NVARCHAR(100),
[salaire] REAL,
[date_debut] DATETIME,
[tache] NVARCHAR(100)
);
ALTER TABLE [Employe] ADD CONSTRAINT [PK_Employe] PRIMARY KEY ([ID]);
The table PRODUCTION I want to create :
create table production(
ID int not null identity(1,1),
date_prod Datetime,
emp collection (emp1,emp2, ...));
Explanation: in the table Production, I will have many employees, so I want to insert them in one line of the entry.
Any idea?
Related
Consider this table
CREATE TABLE employee
(
employee_number INT PRIMARY KEY,
employee_name NVARCHAR(100),
employee_year INT,
manager_employee_number INT,
salary INT,
FOREIGN KEY(manager_employee_number)
REFERENCES employee(employee_number)
);
I want to add a constraint which every employee's employee_year is less than his manager's and we know every manager is an employee himself. So I wrote this:
ALTER TABLE employee
ADD CONSTRAINT CK_EmployeeYearLessThanManager
CHECK (employee_year <= (SELECT m.employee_year
FROM employee
WHERE m.employee_number = manager_employee_number ));
I get this error:
Subqueries are not allowed in this context. Only scalar expressions are allowed
Is there any possible way to write such a constraint?
As it can be seen from the error message, you cannot implement it as a subquery, but as a work around you can create a scalar-valued user defined function and call it from the check constraint. Here is an example:
CREATE TABLE employee
(
employee_number INT PRIMARY KEY,
employee_name NVARCHAR(100),
employee_year INT,
manager_employee_number INT,
salary INT,
FOREIGN KEY(manager_employee_number)
REFERENCES employee(employee_number)
);
GO
CREATE FUNCTION dbo.get_manager_hire_year(#manager_employee_number INT)
RETURNS INT
AS
BEGIN
DECLARE #e_year int;
SELECT #e_year = employee_year
FROM employee
WHERE employee_number = #manager_employee_number;
RETURN #e_year
END
GO
ALTER TABLE employee
ADD CONSTRAINT CK_EmployeeYearLessThanManager
CHECK (employee_year <= dbo.get_manager_hire_year(manager_employee_number))
I'm frankly new to sql and this is a project I'm doing.
I would like to know if there's a way to connect one column in one table to another table when creating tables. I know of the join method to show results of, but I want to minimized my code as possible.
CREATE TABLE players (
id INT PRIMARY KEY, -->code I want connect with table match_record
player_name CHARACTER
);
CREATE TABLE match_records (
(id INT PRIMARY KEY /*FROM players*/), --> the code I want it to be here
winner INT,
loser INT
);
CREATE TABLE players (
id INT not null PRIMARY KEY, -->code I want connect with table match_record
player_name CHARACTER
);
CREATE TABLE match_records (
id INT not null PRIMARY KEY references players(id), --> the code I want it to be here
winner INT,
loser INT
);
this way you restrict that match_records.id is only from players.id:
t=# insert into match_records select 1,1,0;
ERROR: insert or update on table "match_records" violates foreign key constraint "match_records_id_fkey"
DETAIL: Key (id)=(1) is not present in table "players".
So I add players:
t=# insert into players(id) values(1),(2);
INSERT 0 2
And now it allows insert:
t=# insert into match_records select 1,1,0;
INSERT 0 1
update
https://www.postgresql.org/docs/current/static/app-psql.html#APP-PSQL-PROMPTING
%#
If the session user is a database superuser, then a #, otherwise a >.
(The expansion of this value might change during a database session as
the result of the command SET SESSION AUTHORIZATION.)
in this way:
CREATE TABLE new_table as SELECT id,... from old_table where id = 1;
Hi I have this table Cars:
MODEL nvarchar(20)
STYLE nvarchar(20)
ENGINE nvarchar(5)
CAPACITY smallint
MAX_SPEED smallint
PRICE smallmoney
MARKET nvarchar(20)
COMPETITOR nvarchar(20)
And I would like to split it into 3 tables via SQL query:
Cars:
MODEL nvarchar(20)
STYLE nvarchar(20)
MAX_SPEED smallint
PRICE smallmoney
Engine:
ENGINE nvarchar(5)
CAPACITY smallint
Market:
MARKET nvarchar(20)
COMPETITOR nvarchar(20)
So was wandering how this would be done using sql commands, thanks
Easiest way. Select... Into will create new tables:
SELECT DISTINCT
ENGINE,
CAPACITY
INTO Engine
FROM CARS
SELECT DISTINCT
MARKET,
COMPETITOR
INTO Market
FROM CARS
Then just drop the defunct columns from the original table. Eg
ALTER TABLE Cars DROP COLUMN ENGINE
ALTER TABLE Cars DROP COLUMN CAPACITY
ALTER TABLE Cars DROP COLUMN MARKET
ALTER TABLE Cars DROP COLUMN COMPETITOR
This will do specifically what you are asking. However, I'm not sure that is what you want - there is then no reference from the car to the engine or market details - so information is lost.
If "ENGINE" and "MARKET" define the keys of the new table, I'd suggest leaving those columns on the car table as foreign keys. Eg only DROP Capacity and Competitor.
You may wish to create the primary key on the new tables too. Eg:
ALTER TABLE ENGINE ADD CONSTRAINT [PK_Engine] PRIMARY KEY CLUSTERED ENGINE ASC
Run this....
create table Engine
(
EngineId int identity(1,1) not null primary key,
Engine nvarchar(5) not null,
Capacity smallint not null
)
go
insert into Engine
(Engine, Capacity)
(select distinct Engine,Capacity from Cars)
go
alter table Cars
add EngineId int null
go
update Cars
set Cars.EngineId = e.EngineId
from Engine e where e.Engine = Cars.Engine
go
create table Market
(
Id int identity(1,1) not null primary key,
Market nvarchar(20) not null,
Competitor nvarchar(20) not null
)
go
insert into Market
(Market, Competitor)
(select distinct Market,Competitor from Cars)
go
alter table Cars
add MarketId int null
go
update Cars
set Cars.MarketId = m.MarketId
from Market m where m.Market = Cars.Market
go
alter table Cars
drop column Market;
alter table Cars
drop column Competitor;
alter table Cars
drop column Engine;
alter table Cars
drop column Capacity;
To normalize these tables you will firstly need to create new tables, write SQL to insert the data into the new tables and then alter the original table.
See http://technet.microsoft.com/en-us/library/ms174979.aspx
and http://technet.microsoft.com/en-us/library/dd776381(v=sql.105).aspx and http://msdn.microsoft.com/en-us/library/ms190273.aspx
Are Foreign Keys in SQL Server 2008 are automatically indexed with a value? For Example. if I add a value in my Primary key (or auto incremetend) in may parent table will the table that has a foreign key referenced to that key will automatically have the same value? or I Have to do it explicitly?
No, if you create a foreign key in a child table, it will not automatically get populated when a parent row gets inserted. If you think about this it makes sense. Let's say you have a table like:
CREATE TABLE dbo.Students
(
StudentID INT IDENTITY(1,1) PRIMARY KEY,
Name SYSNAME
);
CREATE TABLE dbo.StudentLoans
(
LoanID INT IDENTITY(1,1) PRIMARY KEY,
StudentID INT FOREIGN KEY REFERENCES dbo.Students(StudentID),
Amount BIGINT -- just being funny
);
What you are suggesting is that when you add a row to Students, the system should automatically add a row to StudentLoans - but what if that student doesn't have a loan? If the student does have a loan, what should the amount be? Should the system pick a random number?
Typically what will happen in this scenario is that you'll be adding a student and their loan at the same time. So if you know the loan amount and the student's name, you can say:
DECLARE
#Name SYSNAME = N'user962206',
#LoanAmount BIGINT = 50000,
#StudentID INT;
INSERT dbo.Students(Name)
SELECT #Name;
SELECT #StudentID = SCOPE_IDENTITY();
INSERT dbo.StudentLoans(StudentID, Amount)
SELECT #StudentID, #LoanAmount;
I've created a insert stored procedure with two tables like in the exapmle:
Table NameAge
CREATE TABLE [dbo].[Assignment3_NameAge]
(
userID int PRIMARY KEY IDENTITY(1,1),
Name varchar(255) NOT NULL,
Age int NOT NULL
)
Table Hobbies
CREATE TABLE [dbo].[Assignment3_Hobbies]
(
hobbiesID int Identity(1,1) Primary Key,
userID int Foreign Key references Assignment3_NameAge(userID),
hobbies varchar(255) NOT NULL,
)
Insert Stored Procedure
CREATE PROCEDURE [dbo].p_Assignment3Join_ins
#Name nvarchar(100),
#Age int,
#Hobbies nvarchar(100)
AS
INSERT INTO [TABLE].[dbo].[Assignment3_NameAge]
([Name]
,[Age])
VALUES (#Name,#Age)
INSERT INTO [TABLE].[dbo].[Assignment3_Hobbies]
([Hobbies])
VALUES (#Hobbies)
The problem is that when i run the stored procedure the table Hobbies has a null value for userid(the foreign key)
What am i doing wrong?
You should provide the key of the Assignment3_NameAge value you want to insert into Assignment3_Hobbies.
If you want the last inserted you can use SCOPE_IDENTITY() from SQL Server(if you're using SQL Server) or equivalent. It will give you the last inserted value from Assignment3_NameAge
I am guessing this is SQL Server based on the IDENTITY column. Correct?
The first insert creates a user, but there is no user ID being set on the insert of the hobby. You need to capture the identity value from the first insert to be used in the second insert. Have you gon over the system functions available?
You're not supplying a value for it, SQL won't automagically fill the value in for you even though you've created a Foreign Key relationship. It's your job to populate the tables.