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;
Related
I have 3 tables is shown this tables:
table A
A(
code1
.
.
.
)
table B
B(
code2
.
.
.
)
table C
C(
code3
.
.
.
)
I want to be unique between code1,code2,code3 of this tables.
How do i recieve to my goal in oracle?
Does any syntax of oracle exist about this problem?
Based on materialized view.
P.s.
The code is not validated.
I currently have access only to oracle XE 11gR2, so I'm not able to use the materialized view log feature.
create table A (code int primary key);
create table B (code int primary key);
create table C (code int primary key);
create materialized view log on a with primary key;
create materialized view log on b with primary key;
create materialized view log on c with primary key;
create materialized view ABC_MV
refresh fast
as
select code from A
union all select code from B
union all select code from C
;
alter table ABC_MV add unique (code);
You can do that with trigger.
CREATE OR REPLACE TRIGGER table1_check
BEFORE INSERT OR UPDATE ON table1
FOR EACH ROW
BEGIN
IF EXISTS (
SELECT attribute FROM table2
WHERE attribute = :NEW.attribute
) THEN
RAISE_APPLICATION_ERROR(-20001,
'Already exist in table2');
END IF;
END;
/
You can modify it to check in more tables as well.
Using a 4th table
create table ABC (tab char(1) not null ,code int primary key, unique (tab,code));
create table A (tab char(1) as ('A') virtual not null,code int primary key,foreign key (tab,code) references ABC(tab,code));
create table B (tab char(1) as ('B') virtual not null,code int primary key,foreign key (tab,code) references ABC(tab,code));
create table C (tab char(1) as ('C') virtual not null,code int primary key,foreign key (tab,code) references ABC(tab,code));
insert into ABC (tab,code) values ('A',1);
insert into A (code) values (1);
insert into A (code) values (1);
[Code: 1, SQL State: 23000] ORA-00001: unique constraint (SYS.SYS_C0012834) violated
insert into B (code) values (1);
[Code: 2291, SQL State: 23000] ORA-02291: integrity constraint
(SYS.SYS_C0012839) violated - parent key not found
I have the following two tables:
CREATE TABLE test1
(
ID int IDENTITY UNIQUE,
length int not null
)
CREATE TABLE test2
(
ID int IDENTITY UNIQUE,
test1number int references test1(ID),
distance int not null
)
Example: lets insert into test1 values 1 and 100 (ID=1 and length=100). Now lets insert into test2 values 1 as ID and test1number=1 as reference from test1. I want to create a constraint which will not allow to write distance bigger than 100 (length from test1).
Any other way than procedure?
If this is for individual rows, and we don't need to assert some property about all rows with the same test1number values then one way to do it is this:
CREATE TABLE test1
(
ID int IDENTITY UNIQUE,
length int not null,
constraint UQ_test1_Length_XRef UNIQUE (ID,Length)
)
go
CREATE TABLE _test2
(
ID int IDENTITY UNIQUE,
test1number int references test1(ID),
_test1length int not null,
distance int not null,
constraint FK_test2_test1_length_xref foreign key (test1number,_test1length)
references test1 (ID,length) on update cascade,
constraint CK_length_distance CHECK (distance <= _test1length)
)
go
create view test2
as
select ID,test1number,distance from _test2
go
create trigger T_I_t2 on test2
instead of insert
as
insert into _test2(test1number,_test1length,distance)
select test1number,length,distance
from inserted i inner join test1 t on i.test1number = t.id
go
We only need the view and trigger if you're trying to hide the existence of this extra column in the _test2 table from your users.
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 have a SQL table set that looks like this
create table foo (
id int primary key asc,
data datatype );
create table bar (
id int primary key asc,
fk_foo int,
foreign key(foo_int) references foo(id));
Now, I want to insert a record set.
insert into table foo (data) values (stuff);
But wait - to get Bar all patched up hunkydory I need the PK from Foo. I know this is a solved problem.
What's the solution?
try this
SELECT last_insert_rowid()
I need help in auto populating the primary key values in foreign key table while inserting data in foreign key table. For Example: I have created table:
create table Patient
(
PatientId int IDENTITY(1,1) primary key,
FirstName varchar(50),
SurName varchar(50),
Gender char(20),
)
Say 5 rows are there in this Patient Table:
Say First Row value is: 1, Priya, Kumari, Female
I have created the Guardians Table:
create table Guardians
(
GuardiansId int identity(1,1) primary key,
PatientId int foreign key references Patient(PatientId),
FirstName varchar(50),
SurName varchar(50),
Gender char(20),
RelationToPatient varchar(50),
)
In this table Insert operations are like this:
insert into Guardians(FirstName, SurName, Gender,RelationToPatient)values('Sumit','Kumar','Male','Wife')
While selecting the Guardians Table PatientId showing NULL values: My query is while inserting the values in Guardians Table PatientId should be auto Populated which will come from Patient Table...
My second problem is: How to create the Identity column as varchar. For example: suppose I want to increment my Guardians Table with 'GRD0001', 'GRD0002', 'GRD0003' like this...
Thanks,
S.D
Your question is not very clear - what exactly do you want to do??
When you insert something into the Guardians table, you want to automatically also insert it into the Patients table? I don't quite follow. Can you make a complete example, maybe??
If you need to capture the insert IDENTITY value from the Patient table, do this:
DECLARE #NewPatientID INT
INSERT INTO dbo.Patient(fields) VALUES(.......)
SET #NewPatientID = SCOPE_IDENTITY()
INSERT INTO dbo.Guardians(PatientId, ......) VALUES(#NewPatientID, ......)
As for your second question: leave you GuardiansId IDENTITY as it is (only an INT column can be an IDENTITY and you want to keep that - trust me!) and add a computed column to your table:
ALTER TABLE dbo.Guardians
ADD GuardianIDWithPrefix AS
'GDR' + RIGHT('0000' + CAST(GuardiansId AS VARCHAR(4)), 4) PERSISTED
Since it's a PERSISTED field, you can even index on it and use it like a normal field in every respect.
That should do the trick!