I'm on Postgresql 13.
I want a table(rooms) that assume the default value of "1" if I delete from building which is the "parent table"
This is my sql code
DROP TABLE rooms;
DROP TABLE buildings;
CREATE TABLE buildings (
building_no INT default 1 primary key,
building_name VARCHAR(255),
address VARCHAR(255));
CREATE TABLE rooms (
room_no INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
room_name VARCHAR(255),
building_no INT default 1,
FOREIGN KEY (building_no) REFERENCES buildings (building_no) ON DELETE SET default );
I insert the values into the tables
insert into buildings values (1,'Building1','Street 33');
insert into buildings values (2,'Build-B','Street 34');
insert into rooms values (1,'Room 1',1);
insert into rooms values (2,'Room 2',2);
Then I delete from buildings
delete from buildings;
When I delete from buildings instead of make the default value of 1 as I ask it set the value NULL.
test=> select * from rooms;
room_no | room_name | building_no
---------+-----------+-------------
1 | Room 1 |
2 | Room 2 |
What's wrong in my sql code?
By deleting all of the records in buildings, the default value of 1 in the rooms table violates the FK constraint. Therefore, it's going to set it to NULL. If you were to delete all buildings EXCEPT building 1, you will not encounter the behavior you are describing.
Related
I use 4 table in database.
Example:
Create table applicant(
Id int not null primary key,
IdName integer
idSkill integer,
idContact integer
Constraint initial foreign key (idName) References Initiale(id)
CONSTRAINT contacT foreign key (idContact) References contact(id)
CONSTRAINT Skills foreign key (idSkill) references skill(id))
Create table Initiale(
Id int not null primary key,
firstname text,
middlename text)
Create table contact(
Id int not null primary key,
phone text,
email text)
Create tabke Skills(
Id int not null primary key,,
Nane text)
I want insert data promptly in 4 table,but i not understand, what get id and insert in applicant.
Create tabke Skills ..... will fail. You should use Create table Skills.
Nor should you have Id int not null primary key,, (two commas), this would fail.
You should very likely be using Id INTEGER PRIMARY KEY not Id int not null primary key.
That is because generally an Id column should be a unique identifier of the row. With SQLite INTEGER PRIMARY KEY has a special meaining whilst INT PRIMARY KEY does not.
That is, if INTEGER PRIMARY KEY is used then the column will be an alias of the rowid column which has to be a unique signed 64 bit integer and importantly if no value is provided when inserting a row then SQLite will assign a unique integer. i.e. the all important Id.
This Id will initially be 1, then likely 2, then likely 3 and so on, although there is no guarantee that the Id will be monotonically increasing.
There are additional errors, mainly comma's omitted. The following should work :-
CREATE TABLE IF NOT EXISTS applicant(
Id INTEGER PRIMARY KEY,
IdName integer,
idSkill integer,
idContact integer,
Constraint initial foreign key (idName) References Initiale(id),
CONSTRAINT contacT foreign key (idContact) References contact(id),
CONSTRAINT Skills foreign key (idSkill) references Skills(id));
Create table IF NOT EXISTS Initiale(
Id INTEGER PRIMARY KEY,
firstname text,
middlename text);
Create table IF NOT EXISTS contact(
Id INTEGER PRIMARY KEY,
phone text,
email text);
Create table IF NOT EXISTS Skills(
Id INTEGER PRIMARY KEY,
Nane text);
You could then insert data along the lines of :-
INSERT INTO Initiale (firstname,middlename) -- Note absence of Id so SQLite will generate
VALUES
('Fred','James'), -- very likely id 1
('Alan','Roy'), -- very likely id 2
('Simon','Gerorge')-- very likely id 3
;
INSERT INTO contact -- alternative way of getting Id generated (specify null for Id)
VALUES
(null,'0123456789','email01#email.com'), -- very likely id 1
(null,'0987654321','email02#email.com'), -- very likely id 2
(null,'3333333333','email03.#email.com') -- very likely id 3
;
INSERT INTO Skills (Nane)
VALUES
('Skill01'),('Skill02'),('Skill03') -- very likely id's 1,2 and 3
;
INSERT INTO applicant (IdName,idSkill,idContact)
VALUES
-- First applicant
(2, -- Alan Roy
3, -- Skill 3
1), -- Contact 0123456789 )
-- Second Applicant
(3, -- Simon George
3, -- Skill 3
2), -- Contact 0987654321 )
-- Third Applicant
(2, -- Alan Roy again????
1, -- Skill 1
3), -- contact 3333333333)
(1,1,1) -- Fred James/ Skill 1/ Contact 0123456789
--- etc
;
Noting that Rows on the Initiale, Contact and Skills table MUST exists before insertions can be made into the Applicant table.
You could then run a query such as :-
SELECT * FROM applicant
JOIN Initiale ON Initiale.Id = idName
JOIN contact ON contact.Id = idContact
JOIN Skills ON Skills.Id = idSkill
This would result in (using the data as inserted above) :-
table description
# \d invites;
Table "public.invites"
Column | Type | Modifiers
-----------------------+-----------------------------+---------------------
id | integer | not null default
email | character varying |
key | character varying |
sender_user_id | integer | not null
receiver_user_id | integer |
Indexes:
"invites_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
"fk_invites_receiver_user_id"
FOREIGN KEY (receiver_user_id) REFERENCES users(id)
"fk_invites_sender_user_id"
FOREIGN KEY (sender_user_id) REFERENCES users(id)
you can see Foreighn Key "fk_invites_receiver_user_id" FOREIGN KEY (receiver_user_id) REFERENCES users(id).
But the records for user with pk is absent in the parent table, where in the reference table fk is exists.
# select id from users where id = 958;
id
----
(0 rows)
select count(*) from invites where receiver_user_id = 958;
count
-------
1
(1 row)
the question is how it can be, simple way to fix the conflicts is delete wrong records, but want to exclude such situation in the future, and when i try to restore the data there is an error:
DETAIL: Key (receiver_user_id)=(958) is not present in table "users".
Command was: ALTER TABLE ONLY invites
ADD CONSTRAINT fk_invites_receiver_user_id
FOREIGN KEY (receiver_user_id) REFERENCES users(id);
P.S.
database=# select version();
version
------------------------------------------------------------------------
PostgreSQL 9.4.14 on x86_64-unknown-linux-gnu,
compiled by gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4, 64-bit
Create fail
-- tmp schema
-- \i tmp.sql
-- tables
CREATE TABLE users
(id serial NOT NULL PRIMARY KEY
, name text
);
CREATE TABLE refs
( user_from INTEGER NOT NULL
, user_to INTEGER NOT NULL
, msg text
);
-- data
INSERT INTO users(name) VALUES ('Alice'), ('Bob');
INSERT INTO refs VALUES (1,2), (1,3);
-- FK constraints
ALTER TABLE refs
ADD CONSTRAINT bad_user_from
FOREIGN KEY (user_from) references users(id);
ALTER TABLE refs
ADD CONSTRAINT bad_user_to
FOREIGN KEY (user_to) references users(id)
NOT VALID ; -- <<--HERE
-- This should fail; user=3 does not exist
INSERT INTO refs VALUES (3,2), (2,3);
Repair
-- "repair" the broken refs (by introducing a dummy row)
INSERT INTO users(id,name) VALUES (0, 'NoName');
-- Make the bad FKs point to the dummy row
UPDATE refs r
SET user_to =0
WHERE NOT EXISTS(
SELECT *
FROM users u
WHERE u.id= r.user_to
);
UPDATE refs r
SET user_from =0
WHERE NOT EXISTS(
SELECT *
FROM users u
WHERE u.id= r.user_from
);
SELECT * FROM refs r
JOIN users u0 ON u0.id= r.user_from
JOIN users u1 ON u1.id= r.user_to
;
INSERT INTO users(name) VALUES ('NewName');
-- see what we'v got
SELECT * FROM users;
SELECT* FROM refs r
JOIN users u0 ON u0.id= r.user_from
JOIN users u1 ON u1.id= r.user_to;
Validate constraint
\d refs
\d users
-- enforce the constraint
ALTER TABLE refs
VALIDATE CONSTRAINT bad_user_to; -- <<-- HERE
-- check if valid
\d refs
\d users
-- This should not fail; user=3 does exist now
INSERT INTO refs VALUES (3,2), (2,3);
The answer is unfortunately “data corruption”.
You should delete the offending row, dump the database with pg_dumpall and restore it into a fresh cluster created with initdb.
You should also try to find out what caused the data corruption. Did you have any crashes recently? Could it be that you have unreliable storage or hardware problems? Anything weird in the database log?
To exclude such problems as much as possible, always use the latest fixpack for your PostgreSQL version and use reliable hardware.
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;
I'm having trouble from Inserting 1 Primary Value (Increment) of TABLE to another TABLE (Foreign Key)
Table 1 has the Primary key of Student Number; if i enter values for last and first name from TABLE 1 then the student number will automatically giving it's own value because of Increment, and else if i entered from TABLE 2, I want the value of Student Number from TABLE i will increment even the value of Last and First name if TABLE 1 is NULL
Table 1
(PK)Student_# | Last_Name | First_Name
...........1...........|........a..........|..........b.......
...........2...........|........c..........|..........b.......
Table 2
(FK)Student_# | Year_Level | Section
...........NULL................|..........2nd Year......|.....C1 .........
...........NULL................|..........3rd Year......|.....D1 .........
Needed
(FK)Student_# | Year_Level | Section
..............1...................|..........2nd Year......|.....C1 .........
..............2...................|..........3rd Year......|.....D1 .........
It sounds to me that you need a primary key with an identity seed on table2 and also a foreign key to the student table:
(PK/Identity) Table2ID | (FK)Student_# | Year_Level | Section
This way you can insert the student_# when you insert the record into table 2 and also be able to give each row in table2 a unique identifier
CREATE TABLE Table2
(
Table2ID INT IDENTITY(1,1) PRIMARY KEY
,Student_# INT NOT NULL FOREIGN KEY REFERENCES Table1(Student_#)
,Year_Level NVARCHAR(255) --Use whatever data type you need
,Section NVARCHAR(255) --Use whatever data type you need
)
I have assumed you are using sql server as you have not specified in your question. You may need to change this query for a different RDBMS.
I'm using SQL Server 2005 and wish to create a number address records, updating the contact records with the new Id's:
Take the following tables
create table contact(id int primary key identity, home_address_id int, work_address_id int)
create table address(id int primary key identity, street varchar(25), number int)
And foreign keys:
ALTER TABLE dbo.contact ADD CONSTRAINT FK_contact_address1 FOREIGN KEY (home_address_id) REFERENCES dbo.address(id)
ALTER TABLE dbo.contact ADD CONSTRAINT FK_contact_address2 FOREIGN KEY (work_address_id) REFERENCES dbo.address(id)
some dummy data
insert into contact default values
insert into contact default values
insert into contact default values
How can I insert a default empty address record for all contacts who have no home address, and update the home_address_id in one go?
The first part is simple:
insert into address(street) select null from contact where home_address_id is null
I can even get the newly create address id's:
declare #addressTable table(id int)
insert into address(street)
OUTPUT INSERTED.Id INTO #addressTable
select null from contact where home_address_id is null
Here's the new id's
select * from #addressTable
But how to update the contact table with these new Id's?
If possible, I would suggest normalizing your database by adding a Contact_Addresses table:
CREATE TABLE Contact_Addresses
(
contact_id INT NOT NULL,
address_id INT NOT NULL,
address_type VARCHAR(10) NOT NULL,
CONSTRAINT PK_Contact_Addresses PRIMARY KEY CLUSTERED (contact_id, address_id, address_type),
CONSTRAINT FK_ContactAddresses_Contacts (contact_id) REFERENCES Contacts (id),
CONSTRAINT FK_ContactAddresses_Addresses (address_id) REFERENCES Addresses (id),
CONSTRAINT CK_ContactAddresses_address_type CHECK address_type IN ('HOME', 'WORK')
)
Next, I would suggest not putting "dummy" records in your database. It's going to end up causing headaches down the road. The database should contain an accurate record of the data in your system. If you want to display some value by default when no address exists in the system for a contact then handle that in your UI.
If you really must though, then the following code should do the trick:
;WITH C_CTE AS
(
SELECT
id,
home_address_id,
ROW_NUMBER() OVER(ORDER BY id) AS seq
FROM
Contacts
),
(
SELECT
id,
ROW_NUMBER() OVER(ORDER BY id) AS seq
FROM
Addresses
)
UPDATE
C_CTE
SET
home_address_id = A.id
FROM
C_CTE C
INNER JOIN A_CTE A ON A.seq = C.seq
I would do it from the moment you get a new contact, thusly:
[receive contact information]
//prior to inserting contact
declare #homeAddress int, #workAddress int
[insert home address here (real or default based on input)]
set #homeAddress = ##Identity
[insert work address here (real or default)]
set #workAddress = ##Identity
[insert contact here referencing #homeAddress & #workAddress]
For the stuff already in your table, you're going to have to associate all of your null value ids to a contact id. Or, you could clear out your null value addresses, and modify the above statement to an update somehow (brain's not working at the moment, so all I'm coming up with is a cursor, and cursors are evil).