So I don't understand why I cannot insert data in my table that have foreign constraint keys or even modify anything in it.
Here is an example of the tables that are created. I am trying to insert data in the addresses table:
///////////////////////ADDRESSES TABLE ////////////////////////
CREATE TABLE IF NOT EXISTS addresses (
id INT NOT NULL AUTO_INCREMENT,
addressline1 VARCHAR(255) NOT NULL,
addressline2 VARCHAR(255) NOT NULL,
postcode VARCHAR(255) NOT NULL,
phonenumber INT(13) NOT NULL,
country_id INT NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY (country_id) REFERENCES countries(id)
ON UPDATE CASCADE
ON DELETE RESTRICT
) ENGINE=InnoDB ";
///////////////////////COUNTRIES TABLE ////////////////////////
CREATE TABLE IF NOT EXISTS countries (
id INT NOT NULL AUTO_INCREMENT,
countryname VARCHAR(255) NOT NULL,
PRIMARY KEY (id)
)
The issue here is that you are trying to insert into a referencing table (addresses) when the referenced entry (the country you reference) does not exist. That's what's triggering the FOREIGN KEY CONSTRAINT exception.
Try first inserting some countries into the countries table, then inserting some addresses where you reference those countries you entered in the first step.
As for your second question, that's a choice for you to make. I would probably choose to have the User have an Address (address field in the User table), but some of that depends on how the data is being used/updated.
Have a quick look through this resource if you're new to relational database design. It covers (in brief) topics like relationship types, key constraints, and normal forms.
Related
I am having trouble figuring out the best design for my many-to-many relationship in my database. My project allows users to create what we are calling log alarms. A log alarm will check if a given log meets certain criteria and, if so, it will send a message to an AWS SNS topic. What I want to do is relate log alarms to AWS SNS topics. I also want to relate which user assigned that log alarm to that AWS SNS topic.
I have a table class XRefUserLogAlarmSNSTopic. It has three foreign keys. The goal of this table is to relate which SNS topics are related to what log alarms and to indicate which user made the relation. This seems rather messy to me and I get all sorts of errors when I try to create new log alarms or join tables in Spring JPA. My question is, is there are better database structure for what I am trying to achieve
UserId INT NOT NULL AUTO_INCREMENT,
Username VARCHAR(50) NOT NULL,
Password TEXT NOT NULL,
Email VARCHAR(255) NOT NULL,
Dashboard LONGTEXT NOT NULL,
PRIMARY KEY (UserId),
UNIQUE (Username),
UNIQUE (Email)
);
CREATE TABLE SNSTopics (
SNSTopicId INT NOT NULL AUTO_INCREMENT,
TopicName VARCHAR(50) NOT NULL,
TopicArn VARCHAR(255) NOT NULL,
PRIMARY KEY (SNSTopicId),
UNIQUE (TopicName),
UNIQUE (TopicArn)
);
CREATE TABLE LogGroups (
LogGroupId INT NOT NULL AUTO_INCREMENT,
Name VARCHAR(255) NOT NULL,
PRIMARY KEY (LogGroupId),
UNIQUE (Name)
);
CREATE TABLE Keywords (
KeywordId INT NOT NULL AUTO_INCREMENT,
Word VARCHAR(70),
PRIMARY KEY (KeywordId),
UNIQUE (Word)
);
CREATE TABLE LogAlarms (
LogAlarmId INT NOT NULL AUTO_INCREMENT,
LogLevel VARCHAR(5) NOT NULL CHECK (LogLevel IN ('TRACE', 'DEBUG', 'INFO', 'WARN', 'ERROR')),
Comparison VARCHAR(2) CHECK (Comparison IN ('==', '<', '<=', '>', '>=')),
AlarmName VARCHAR(255) NOT NULL,
KeywordRelationship CHAR(3) CHECK (KeywordRelationship IN ('ANY', 'ALL', NULL)),
PRIMARY KEY (LogAlarmId),
UNIQUE (AlarmName)
);
CREATE TABLE MetricAlarms (
MetricAlarmId INT NOT NULL AUTO_INCREMENT,
AlarmArn VARCHAR(100) NOT NULL,
PRIMARY KEY (MetricAlarmId),
UNIQUE (AlarmArn)
);
CREATE TABLE XRefUserMetricAlarm (
UserMetricAlarmId INT NOT NULL AUTO_INCREMENT,
UserId INT NOT NULL,
MetricAlarmId INT NOT NULL,
PRIMARY KEY (UserMetricAlarmId),
FOREIGN KEY (UserId) REFERENCES Users(UserId) ON DELETE CASCADE,
FOREIGN KEY (MetricAlarmId) REFERENCES MetricAlarms(MetricAlarmId) ON DELETE CASCADE,
UNIQUE (UserId, MetricAlarmId)
);
CREATE TABLE XRefLogAlarmLogGroup (
LogAlarmLogGroupId INT NOT NULL AUTO_INCREMENT,
LogAlarmId INT NOT NULL,
LogGroupId INT NOT NULL,
PRIMARY KEY (LogAlarmLogGroupId),
FOREIGN KEY (LogAlarmId) REFERENCES LogAlarms(LogAlarmId) ON DELETE CASCADE,
FOREIGN KEY (LogGroupId) REFERENCES LogGroups(LogGroupId) ON DELETE CASCADE,
UNIQUE (LogAlarmId, LogGroupId)
);
CREATE TABLE XRefLogAlarmKeyword (
LogAlarmKeywordId INT NOT NULL AUTO_INCREMENT,
LogAlarmId INT NOT NULL,
KeywordId INT NOT NULL,
PRIMARY KEY (LogAlarmKeywordId),
FOREIGN KEY (LogAlarmId) REFERENCES LogAlarms(LogAlarmId) ON DELETE CASCADE,
FOREIGN KEY (KeywordId) REFERENCES Keywords(KeywordId) ON DELETE CASCADE,
UNIQUE (LogAlarmId, KeywordId)
);
CREATE TABLE XRefUserLogAlarmSNSTopic (
UserLogAlarmSNSTopicId INT NOT NULL AUTO_INCREMENT,
LogAlarmId INT NOT NULL,
SNSTopicId INT NOT NULL,
UserId INT NOT NULL,
PRIMARY KEY (UserLogAlarmSNSTopicId),
FOREIGN KEY (LogAlarmId) REFERENCES LogAlarms(LogAlarmId) ON DELETE CASCADE,
FOREIGN KEY (SNSTopicId) REFERENCES SNSTopics(SNSTopicId) ON DELETE CASCADE,
FOREIGN KEY (UserId) REFERENCES Users(UserId) ON DELETE CASCADE,
UNIQUE (LogAlarmId, SNSTopicId, UserId)
);```
To match your description, your XRefUserLogAlarmSNSTopic is not correct.
You do not actually want to link three entities, just two: you want to relate log alarms to AWS SNS topics (which are the two values that identify that relationship), and then add a user as an attribute to that relation. Although in this case this specific attribute refers to another entity, it is logically not fundamentally different than e.g. a timestamp that stores when that relationsship was created (by that user).
The difference to your current table is the primary key/unique key: your current table allows you to add a relationship between an alarm and a topic several times if different users add them, as only (alarm, topic, user) needs to be unique, instead of (alarm, topic) being unique, and user being an attribute to that relation.
I would also consider if you want an ON DELETE CASCADE for the UserId column. While cascading for LogAlarmId and SNSTopicId makes sense, it's not obvious that you need to remove all relations when you delete the user that created them (although it of course depends on your requirements). It may be better to just set them to null. So I would propose a table like
CREATE TABLE XRefLogAlarmSNSTopic ( -- user not part of table name
LogAlarmSNSTopicId INT NOT NULL AUTO_INCREMENT,
LogAlarmId INT NOT NULL,
SNSTopicId INT NOT NULL,
UserId INT NULL, -- null
PRIMARY KEY (UserLogAlarmSNSTopicId),
FOREIGN KEY (LogAlarmId) REFERENCES LogAlarms(LogAlarmId) ON DELETE CASCADE,
FOREIGN KEY (SNSTopicId) REFERENCES SNSTopics(SNSTopicId) ON DELETE CASCADE,
FOREIGN KEY (UserId) REFERENCES Users(UserId) ON DELETE SET NULL, -- set null
UNIQUE (LogAlarmId, SNSTopicId) -- user not part of primary key candidate
)
It is obviously also possible that you want that 3-way-relationship, e.g. each user creates their own alarm-topic-relations, in which case your table would be correct, just your description would not be precise enough.
I am trying to create three tables such as associate, manager and attendance. The attendance table should be having employee and manager details from the other two table which should enable marking the attendance. I created this SQL script. I'm not sure where I am making mistake.
CREATE TABLE associate (
id INT NOT NULL,
idmanager INT NOT NULL,
emp_id DATE NOT NULL,
emp_name VARCHAR(25) NOT NULL,
FOREIGN KEY (id) REFERENCES attendance (associate_id) ON DELETE CASCADE,
FOREIGN KEY (idmanager) REFERENCES attendance (manager_idmanager) ON DELETE CASCADE,
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE manager (
id INT NOT NULL,
mgr_usr_id VARCHAR(15) NOT NULL,
mgr_name VARCHAR(25) NOT null,
KEY (id),
KEY (mgr_usr_id),
FOREIGN KEY (id) REFERENCES associate (idmanager) ON DELETE CASCADE,
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE attendance (
sno INT NOT NULL,
manager_idmanager INT NOT NULL,
associate_id INT NOT NULL,
date_stamp DATETIME,
state BIT NOT NULL,
PRIMARY KEY (sno)
) ENGINE=INNODB;
Screenshot
It's an issue of ordering. For example, the first statement executed is
CREATE TABLE associate (
which references attendance. However, the attendance table has not yet been created. Switch the order so that any tables that reference other tables come last.
Alternatively, don't put the FOREIGN KEY constraints in the CREATE statements, but them at the end of your script with ALTER TABLE statements. Consider:
CREATE TABLE associate (
id INT NOT NULL,
idmanager INT NOT NULL,
emp_id DATE NOT NULL,
emp_name VARCHAR(25) NOT NULL,
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE attendance (
sno INT NOT NULL,
manager_idmanager INT NOT NULL,
associate_id INT NOT NULL,
date_stamp DATETIME,
state BIT NOT NULL,
PRIMARY KEY (sno)
) ENGINE=INNODB;
ALTER TABLE associate ADD FOREIGN KEY (id) REFERENCES associate(id) ON DELETE CASCADE;
Edit
The above is just syntax. To model the requested problem consider orthogonality of information. You might also see/hear "normalization." The basic concept is this: have only one copy of your information. The schema should have a single point of authority for all data. For example, if a user has a birthdate, make sure you don't have an ancillary column that also stores their birthday; it's superfluous information and can lead to data errors.
In this case, what is the relationship? What must come first for the other to exist? Can an attendance be had without a manager? How about a manager without attendance? The former makes no sense. In this case then, I would actually use a third table, to form a hierarchy.
Then, consider that maybe roles change in a company. It would not behoove the DB architect to hard code roles as tables. Consider:
CREATE TABLE employee (
id INTEGER NOT NULL AUTO_INCREMENT,
name VARCHAR(25) NOT NULL,
PRIMARY KEY (id)
) ENGINE=INNODB;
CREATE TABLE role (
id INTEGER NOT NULL AUTO_INCREMENT,
name VARCHAR(30) NOT NULL,
description VARCHAR(254) NOT NULL,
PRIMARY KEY( id ),
UNIQUE( name )
) ENGINE=INNODB;
INSERT INTO role (name, description) VALUES
('associate', 'An associate is a ...'),
('manager', 'A manager follows ...');
CREATE TABLE employee_role (
employee_id INTEGER NOT NULL,
role_id INTEGER NOT NULL,
PRIMARY KEY (employee_id, role_id),
FOREIGN KEY (idemployee_id) REFERENCES employee_id (id) ON DELETE CASCADE,
FOREIGN KEY (role_id) REFERENCES role (id) ON DELETE CASCADE
) ENGINE=INNODB;
CREATE TABLE attendance (
sno INTEGER NOT NULL,
employee_id INTEGER NOT NULL,
date_stamp DATETIME,
state BIT NOT NULL,
PRIMARY KEY (sno),
FOREIGN KEY (idemployee_id) REFERENCES employee_id (id) ON DELETE CASCADE
) ENGINE=INNODB;
From this schema, the attendance needs only one foreign key because everyone is an employee. Employee's can have multiple roles, and they can change. Further, role definitions can change without needing to resort to costly DDL statements (data definition layer changes, like ALTER TABLE), and can be modified with simple DML (data manipulation layer changes, like UPDATE TABLE). The former involves rewriting all entries in the tables, and changing schemas, while the latter involves changing individual entries.
I was planning to make 2 tables for user infomation . The first lager table named userInfo has all data . The second smaller table named loginDetails have the minimum data to log in .
My problem is : I could not assign multiple foreign key .
MySQL said:
#1005 - Can't create table `test`.`logindetails` (errno: 150 "Foreign key constraint is incorrectly formed")
Here is code :
CREATE TABLE userInfo
(
userInfoUserNumber INT(255) UNSIGNED AUTO_INCREMENT UNIQUE NOT NULL,
userInfoUserName VARCHAR(255) UNIQUE NOT NULL,
userInfoPassword VARCHAR(255) NOT NULL,
userInfoFirstName VARCHAR(255) NOT NULL,
userInfoLastName VARCHAR(255) NOT NULL,
userInfoPhoneNumber INT(255) UNSIGNED ZEROFILL UNIQUE NOT NULL,
userInfoPlaceWithoutDivision VARCHAR(255) NOT NULL,
userInfoDivision VARCHAR(255) NOT NULL,
userInfoEmail VARCHAR(255) UNIQUE,
userInfoProfilePicture VARCHAR(255),
PRIMARY KEY (userInfoUserNumber)
);
CREATE TABLE loginDetails
(
loginDetailsUserNumber INT(255) UNSIGNED AUTO_INCREMENT UNIQUE NOT NULL,
loginDetailsUserName VARCHAR(255) UNIQUE NOT NULL,
loginDetailsPassword VARCHAR(255) NOT NULL,
loginDetailsPhoneNumber INT(255) UNSIGNED ZEROFILL UNIQUE NOT NULL,
loginDetailsEmail VARCHAR(255) UNIQUE,
PRIMARY KEY (loginDetailsUserNumber) ,
FOREIGN KEY (loginDetailsUserName) REFERENCES userInfo(userInfoUserName)
ON DELETE SET NULL
ON UPDATE CASCADE,
FOREIGN KEY (loginDetailsPassword) REFERENCES userInfo(userInfoPassword)
ON DELETE SET NULL
ON UPDATE CASCADE,
FOREIGN KEY (loginDetailsPhoneNumber) REFERENCES userInfo(userInfoPhoneNumber)
ON DELETE SET NULL
ON UPDATE CASCADE,
FOREIGN KEY (loginDetailsEmail) REFERENCES userInfo(userInfoEmail)
ON DELETE SET NULL
ON UPDATE CASCADE
);
[ In short : suppose my first table has 10 columns , my second table has 5 columns , i want to choose any 4 columns from 1st table and copy to my second table ]
Question 2 :
why this statement is error ? please explain
INSERT INTO userInfo(userInfoUserName,userInfoPassword,userInfoFirstName,userInfoLastName,userInfoPhoneNumber,userInfoPlaceWithoutDivision,userInfoDivision)
VALUES (cat,SHA1(cat),white,cat,01111111111,myplace,mydivision);
You can declare a foreign key only if the column you reference is the leftmost column of a key.
Traditionally, you'd reference only a unique or primary key, but InnoDB (strangely) allows a foreign key to reference any kind of key or partial key.
Your column userInfo.userInfoPassword is not part of any key.
It's not clear what purpose there could be for declaring all those foreign keys. If you want them to cascade, to always remain the same value in the userInfo table, then why are they stored in both tables at all? Just store them in one table.
i want to create a different table (loginDetails) taking 4 columns from userinfo
Why? You don't have to create a different table if you want to fetch a result set with just those four columns. You just specify the columns you want in a query instead of using SELECT *.
SELECT loginDetailsUserNumber,
loginDetailsUserName,
loginDetailsPassword,
loginDetailsPhoneNumber,
loginDetailsEmail
FROM userInfo;
Another option would be to use CREATE VIEW to define a view with those four columns, and then you could use SELECT * from your view.
CREATE VIEW loginDetails AS
SELECT loginDetailsUserNumber,
loginDetailsUserName,
loginDetailsPassword,
loginDetailsPhoneNumber,
loginDetailsEmail
FROM userInfo;
SELECT * FROM loginDetails;
When designing foreign key relationships, you should be linking using primary keys. This would suggest:
CREATE TABLE loginDetails (
loginDetailsUserNumber INT UNSIGNED AUTO_INCREMENT UNIQUE NOT NULL,
loginDetailsUserInfoUserNumber INT UNSIGNED,
loginDetailsUserName VARCHAR(255) UNIQUE NOT NULL,
loginDetailsPassword VARCHAR(255) NOT NULL,
loginDetailsPhoneNumber INT(255) UNSIGNED ZEROFILL UNIQUE NOT NULL,
loginDetailsEmail VARCHAR(255) UNIQUE,
PRIMARY KEY (loginDetailsUserNumber) ,
FOREIGN KEY (loginDetailsUserInfoUserNumber) REFERENCES userInfo(userInfoUserNumber)
ON DELETE SET NULL
ON UPDATE CASCADE,
);
In other words, you can keep the duplicated columns (perhaps a user changes his/her name or password and you want the version associated with the login). BUT, you should be assigning a user number at login and putting that id in the table.
There are many similar question but this is bit different.
I have one table which has one foreign key that will reference to two tables.
I used below query for testing.
CREATE TABLE users
(
id int NOT NULL,
username varchar(255) NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE admins
(
id int NOT NULL,
username varchar(255) NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE info
(
id int NOT NULL,
fullname int NOT NULL,
user_id int,
PRIMARY KEY (id),
FOREIGN KEY (user_id) REFERENCES users(id),
FOREIGN KEY (user_id) REFERENCES admins(id)
);
Above queries works fine.
but when I try to draw model in mysql workbench it create on new field in info table that I don't want. I want user_id should work and show relation as foreign key for users and admins table.
One more thing, am I trying to do that is not well standard? Also suggests a correct way to do it.
Table names used only for example purpose. There is no logic here. I am trying to find solution for one key as foreign key for multiple table and faced issue with mysql work bench.
Try this:
Save your DDL in a file.
Create new model in MySQL Workbench
File > Import > Reverse Engineer MySQL Create Script
Browse to file created in step 1. Ensure that 'Place imported objects on diagram' is selected.
Click 'Execute'
From a data modelling point of view you might be better off specifying a user as an admin by including an extra column on the users table. Hence:
CREATE TABLE users
(
id int NOT NULL,
username varchar(255) NOT NULL,
isAdmin boolean not null default false,
PRIMARY KEY (id)
);
CREATE TABLE info
(
id int NOT NULL,
fullname int NOT NULL,
user_id int,
PRIMARY KEY (id),
FOREIGN KEY (user_id) REFERENCES users(id)
);
I have the following tables (Primary key in bold. Foreign key in Italic)
Customer table
ID---Name---Balance---Account_Name---Account_Type
Account Category table
Account_Type----Balance
Customer Detail table
Account_Name---First_Name----Last_Name---Address
Can I have two foreign keys in the Customer table and how can I implement this in MySQL?
Updated
I am developing a web based accounting system for a final project.
Account Category
Account Type--------------Balance
Assets
Liabilities
Equity
Expenses
Income
Asset
Asset_ID-----Asset Name----Balance----Account Type
Receivable
Receivable_ID-----Receivable Name-------Address--------Tel-----Asset_ID----Account Type
Receivable Account
Transaction_ID----Description----Amount---
Balance----Receivable_ID----Asset_ID---Account Type
I drew the ER(Entity relationship) diagram using a software and when I specify the relationship it automatically added the multiple foreign keys as shown above. Is the design not sound enough?
create table Table1
(
id varchar(2),
name varchar(2),
PRIMARY KEY (id)
)
Create table Table1_Addr
(
addid varchar(2),
Address varchar(2),
PRIMARY KEY (addid)
)
Create table Table1_sal
(
salid varchar(2),`enter code here`
addid varchar(2),
id varchar(2),
PRIMARY KEY (salid),
index(addid),
index(id),
FOREIGN KEY (addid) REFERENCES Table1_Addr(addid),
FOREIGN KEY (id) REFERENCES Table1(id)
)
Yes, MySQL allows this. You can have multiple foreign keys on the same table.
Get more details here FOREIGN KEY Constraints
The foreign keys in your schema (on Account_Name and Account_Type) do not require any special treatment or syntax. Just declare two separate foreign keys on the Customer table. They certainly don't constitute a composite key in any meaningful sense of the word.
There are numerous other problems with this schema, but I'll just point out that it isn't generally a good idea to build a primary key out of multiple unique columns, or columns in which one is functionally dependent on another. It appears that at least one of these cases applies to the ID and Name columns in the Customer table. This allows you to create two rows with the same ID (different name), which I'm guessing you don't want to allow.
Yes, a table have one or many foreign keys and each foreign keys hava a different parent table.
CREATE TABLE User (
user_id INT NOT NULL AUTO_INCREMENT,
userName VARCHAR(100) NOT NULL,
password VARCHAR(255) NOT NULL,
email VARCHAR(255) NOT NULL,
userImage LONGBLOB NOT NULL,
Favorite VARCHAR(255) NOT NULL,
PRIMARY KEY (user_id)
);
and
CREATE TABLE Event (
EventID INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (EventID),
EventName VARCHAR(100) NOT NULL,
EventLocation VARCHAR(100) NOT NULL,
EventPriceRange VARCHAR(100) NOT NULL,
EventDate Date NOT NULL,
EventTime Time NOT NULL,
EventDescription VARCHAR(255) NOT NULL,
EventCategory VARCHAR(255) NOT NULL,
EventImage LONGBLOB NOT NULL,
index(EventID),
FOREIGN KEY (EventID) REFERENCES User(user_id)
);