I'm building a database for a library management system, so I have created three tables: books, members and borrow(describe the relation between the two tables).
for each book I store in the books table, I store it's quantity.
for each member that want to borrow a book, I store his id and the book id in the borrow table.
for every time a member want to borrow a book, I want to check that borrowed quantity is equal or less than the quantity stored for that book in the books table(in case it was more it will rise an error and will not accept the new data) , so I tried to achieve this using a trigger
the problem is that when I try to run the trigger it's not created, and it does not even give an error message, when I try even to see the trigger that is created in the database using the command:(select name from sqlite_master where type = 'trigger';) it does not show any thing
here is the code:
CREATE TABLE books(
book_id INTEGER CHECK (book_id>0999) PRIMARY KEY AUTOINCREMENT,
book_title VARCHAR(20) NOT NULL,
author_name VARCHAR(20),
quantity INT NOT NULL,
genre VARCHAR(20) NOT NULL,
book_place VARCHAR(20) NOT NULL,
UNIQUE(book_title,author_name)
);
CREATE TABLE members(
member_id INTEGER PRIMARY KEY AUTOINCREMENT CHECK(member_id<1000) ,
member_name VARCHAR(20) NOT NULL,
member_phone TEXT NOT NULL UNIQUE
CHECK (LENGTH(member_phone)==11 AND member_phone NOT GLOB '*[^0-9]*'
AND (SUBSTR(member_phone,1,3)=='010' OR SUBSTR(member_phone,1,3)=='011'
OR SUBSTR(member_phone,1,3)=='012' OR SUBSTR(member_phone,1,3)=='015' )),
sub_startDate TEXT NOT NULL CHECK(sub_startDate IS DATE(sub_startDate)),
sub_endDate TEXT NOT NULL CHECK(sub_endDate IS DATE(sub_endDate))
);
CREATE TABLE borrow(
member_id INTEGER NOT NULL,
book_id INTEGER NOT NULL,
borrowed_date TEXT NOT NULL CHECK(borrowed_date IS DATE(borrowed_date)),
return_date TEXT NOT NULL CHECK (return_date IS DATE(return_date)),
FOREIGN KEY(member_id) REFERENCES members(member_id) ON DELETE CASCADE ,
FOREIGN KEY(book_id) REFERENCES books(book_id) ON DELETE CASCADE,
PRIMARY KEY(member_id,book_id)
);
CREATE TRIGGER not_enough_copies
BEFORE INSERT, UPDATE
ON borrow
WHEN
(SELECT((SELECT
COUNT(*)
FROM borrow
WHERE book_id=NEW.book_id)
NOT BETWEEN 1 AND
(SELECT quantity FROM books WHERE books.book_id==NEW.book_id)))
BEGIN
RAISE(ABORT,'ERROR!..This book is not available in the library right now')
END;
Related
In a sqlite3 database I would like to create a trigger on a view so that I can insert data over the view. Inside the trigger I would like to insert something in the tblmedia table. The id of the inserted row should be now also inserted into the tblbook as id.
In sqlite there are no variables. Otherwise I would store the returning value in the variable and would use it in the second query.
Can this even be achieved in sqlite?
Following my sql schema:
CREATE TABLE tblmedia(
id INTEGER PRIMARY KEY NOT NULL,
title VARCHAR NOT NULL,
raiting INTEGER,
file_name VARCHAR NOT NULL,
media_type TEXT NOT NULL
);
CREATE TABLE tblbook(
id INTEGER PRIMARY KEY NOT NULL,
author VARCHAR,
FOREIGN KEY (id) REFERENCES tblmedia(id) ON DELETE CASCADE
);
CREATE VIEW book AS
SELECT
m.id as id,
m.title as title,
b.author as author,
m.raiting as raiting,
m.file_name as file_name
FROM tblbook b
LEFT JOIN tblmedia m ON m.id = b.id;
CREATE TRIGGER insert_book
INSTEAD OF INSERT ON book
BEGIN
INSERT INTO tblmedia(title, raiting, file_name)
VALUES(new.title, new.raiting, new.file_name);
INSERT INTO tblbook(id, author)
VALUES (xx, new.author); -- xx should be the id from the previous insert
END
I want to assure at inserting a manager that department manager start date [DEPARTMENT.mgr_start_date] is coming after his birthdate [EMPLOYEE.bdate],
how can I do that?
CREATE TABLE IF NOT EXISTS EMPLOYEE
(
ssn INT(16) unsigned NOT NULL,
fname VARCHAR(16),
lname VARCHAR(16),
bdate DATE,
address VARCHAR(32),
gender enum('m','f'),
salary decimal(16,2),
Dno VARCHAR(8),
PRIMARY KEY (ssn)
);
CREATE TABLE IF NOT EXISTS DEPARTMENT
(
mgr_ssn INT(16) unsigned,
Dname VARCHAR(32),
mgr_start_date DATE,
Dnumber VARCHAR(8),
PRIMARY KEY (Dnumber),
FOREIGN KEY (mgr_ssn) REFERENCES EMPLOYEE(ssn)
);
You would have to do this with a trigger.
CHECK constraints can reference only columns in the table where the constraint is defined.
The full SQL standard includes a type of constraint called an ASSERTION, which allows multi-table constraints, but MariaDB does not implement this feature of SQL (very few brands of SQL databases do implement it).
CREATE TRIGGER t BEFORE INSERT ON DEPARTMENT
FOR EACH ROW BEGIN
IF NEW.mgr_start_date < (SELECT bdate FROM EMPLOYEE WHERE ssn = NEW.mgr_ssn) THEN
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'manager is way too young';
END IF;
END
Test:
insert into EMPLOYEE set ssn=123, bdate='2021-01-01';
insert into DEPARTMENT set mgr_ssn=123, dnumber='1', mgr_start_date='2010-01-01';
ERROR 1644 (45000): manager is way too young
I am trying to delete a record from table users.
Tried deleteing it with a DELETE-statement (DELETE FROM users WHERE user_id=10" as well as in my DB browser, but I get the above error, specifically it says: "Error deleting record: foreign key mismatch - "games" referencing "groups" (DELETE FROM "main"."users" WHERE rowid IN ('10');)".
Below my schema:
CREATE TABLE users (
user_id INTEGER PRIMARY KEY,
name VARCHAR(255) NOT NULL,
hash VARCHAR(255) NOT NULL,
UNIQUE(name));
CREATE TABLE 'groups' (
'group_name' VARCHAR(255) NOT NULL,
'turn' INTEGER NOT NULL,
'user_id'INTEGER,
FOREIGN KEY ('user_id') REFERENCES 'users'('user_id')
ON UPDATE CASCADE
ON DELETE CASCADE
);
CREATE TABLE games (
game_id INTEGER PRIMARY KEY,
active INTEGER,
turn INTEGER,
group_name VARCHAR(255) NOT NULL,
FOREIGN KEY (turn) REFERENCES groups(turn_id)
ON UPDATE CASCADE
ON DELETE CASCADE,
FOREIGN KEY (group_name) REFERENCES groups(group_name)
ON UPDATE CASCADE
ON DELETE NO ACTION
);
Why is this a problem? user_id is not even a foreign key in 'games'?? Thank you!
The problem in the end was my DB Browser for SQLite (3.11.2) whose GUI allows deletions but they don't actually work. When I tied again in the bash and closed and restarted the DB Browser, the rows were gone. Uninsightful but figured I'd post nonetheless in case anyone else comes across this.
I already checked out this question, and thought I had the answer - but then it didn't look right to me.
I have the following pared down example:
CREATE TABLE pipelines (
name VARCHAR NOT NULL,
owner VARCHAR NOT NULL,
description VARCHAR,
PRIMARY KEY (name, owner),
FOREIGN KEY(owner) REFERENCES user (id)
);
CREATE TABLE tasks (
id INTEGER NOT NULL,
title VARCHAR,
pipeline VARCHAR,
owner VARCHAR,
PRIMARY KEY (id),
FOREIGN KEY(pipeline) REFERENCES pipelines (name),
FOREIGN KEY(owner) REFERENCES pipelines (owner)
);
CREATE TABLE user (
id VARCHAR NOT NULL,
name VARCHAR,
password VARCHAR,
PRIMARY KEY (id)
);
pragma foreign_keys=on;
insert into user values ('wayne', '', '');
insert into pipelines values ('pipey', 'wayne', '');
insert into tasks values (1, 'hello', 'pipey', 'wayne');
When executing this code, it bails out:
$ sqlite3 foo.sq3 '.read mismatch.sql'
Error: near line 27: foreign key mismatch
Through the list in the question I cited:
the parent table (user) exists.
the parent columns (name, owner) exist
the parent columns are, in fact, the primary key (I thought that may have been it originally)
the child table references all of the primary key columns in the parent table
So what in the world could be causing this error?
The documentation says:
Usually, the parent key of a foreign key constraint is the primary key of the parent table. If they are not the primary key, then the parent key columns must be collectively subject to a UNIQUE constraint or have a UNIQUE index.
In the pipelines table, neither the name nor the owner columns are, by themselves, unique.
I guess you actually want to have a two-column foreign key in the tasks table:
FOREIGN KEY(pipeline, owner) REFERENCES pipelines(name, owner)
Sorry for the poor title. I have a query (below) that executes properly and creates an insertion just as I would desire. However, I want to make it smarter by only inserting when the exact combination of three columns. Essentially, the three column tuple is a primary key, but I'm working with the limitation of sqlite's single primary key.
Basic Context
I have 4 tables: Permissions, Roles, Users, Actions
Permissions connects Roles and Users to Actions. The Actions table has a list of available tasks that a User or a user with a Role can perform. So for example, if user_id = 1 can perform a list_folder action (action_id = 1), then the permissions table would have an entry: (id=1, action_id=1, user_id=1, role_id=NULL). Likewise, suppose an owner_role (role_id=1) might have permissions to perform a list_folder action (action_id=1), then the permissions entry might be: (id=2, action_id=1, user_id=NULL, role_id=1).
When I do an insert, I want to make sure that I do not already have that exact combination (e.g. action_id=1, user_id=NULL, role_id=1). And I'm not entirely sure how to write the sql so that I have this setup properly.
Here's my basic insert statement. I need to come up with an insert and a replace statement:
INSERT INTO permissions (
action_id
,role_id
)
SELECT DISTINCT
a.id as "action_id"
,r.id as "role_id"
FROM tmp_permissions tmp
LEFT OUTER JOIN actions a
ON tmp.action_name = a.name
LEFT OUTER JOIN roles r
ON tmp.roles_name = r.name
LEFT OUTER JOIN permissions p
ON p.role_id
Here are some creation sql statements for the tables:
CREATE TABLE permissions (
id INTEGER NOT NULL,
enabled INTEGER,
action_id INTEGER,
user_id INTEGER,
role_id INTEGER,
PRIMARY KEY (id),
FOREIGN KEY(user_id) REFERENCES users (id),
FOREIGN KEY(action_id) REFERENCES actions (id),
FOREIGN KEY(role_id) REFERENCES roles (id)
);
CREATE TABLE actions (
id INTEGER NOT NULL,
enabled INTEGER,
name VARCHAR(50),
permission_ids INTEGER,
PRIMARY KEY (id),
FOREIGN KEY(permission_ids) REFERENCES permissions (id)
);
CREATE TABLE roles (
id INTEGER NOT NULL,
enabled INTEGER,
name VARCHAR(50),
permission_ids INTEGER,
PRIMARY KEY (id),
FOREIGN KEY(permission_ids) REFERENCES permissions (id)
);
CREATE TABLE users (
id INTEGER NOT NULL,
enabled INTEGER,
name VARCHAR(50),
permission_ids INTEGER,
PRIMARY KEY (id),
FOREIGN KEY(permission_ids) REFERENCES permissions (id)
);
Here's a temp table I'm using to store the data in the table while I work with it:
CREATE TABLE tmp_permissions(
roles_name VARCHAR(50),
action_name VARCHAR(50)
);
Here's some data:
#role|action
admin|setup
admin|debug
admin|login
admin|view_user
manager|view_employee
manager|enroll_employee
manager|login
employee|schedule
employee|login
customer|guest_login
customer|change_credentials
guest|guest_login
Thanks in advance!
Add a UNIQUE constraint to the table:
CREATE TABLE permissions(
... ,
UNIQUE (action_id, user_id, role_id)
)
You can then use any of the conflict resolution algorithms to handle duplicates.