Nothing shows when I use select * - mysql

I created some tables but when I want to check if my data is inside it doesn't show anything when
I use select * from Project it just appears null and I don't have null values I'm not sure what I'm doing wrong it just appears that the foreign key is restrict
`create table Department
(
`did integer not null auto_increment,
Dname varchar(50) default 'HR',
location varchar(50) default 'Chicago',
primary key(did)`
);
`create table Employee`
(
Eid integer not null auto_increment,
DepartmentID integer default 5,
Ename varchar(50) default 'Josh',
Erank integer default 2,
Salary real default 5000.00,
primary key(Eid),
foreign key(DepartmentID) references Department(did)
);
/*drop table Project;*/
create table Project
(
Pid integer not null auto_increment,
DepartmentID integer default 5,
Pname varchar(50) default 'Sorting',
budget real default 5000.00,
StartYear integer default 2000,
primary key(Pid),
foreign key(DepartmentID) references Department(did)
);
insert
into Project(DepartmentID, Pname, budget, StartYear)
values(1, 'OS', 5000.00, 2018),
(2, 'Net', 6000.00, 2020);
select *
from Project;


Check this fiddle. There are no rows in Department, so the restraint keeps the insert into Projects from happening. Also, I removed the backticks:
https://dbfiddle.uk/?rdbms=mysql_5.7&fiddle=64f8f0e9cccce2eb2ab77b37fcce54fd


Add COMMIT statements:
create table Project...
commit;
insert into Department values('HR','Chicago');
insert into Department values('Admin','New York');
insert into Project...
commit;
select * from Project;

Related

MySQL: Created Table won't show values?

I'm new to MySQL and I created a table called students with some attributes but when I run Select * From Students it appears as null for each category I'm not sure why
use practice;
create table Students(
sid integer default 1,
sname varchar(50) default 'Joe',
GPA real default 1.7,
dateOfBirth date default (2000-12-12),
primary key(sid)
);
select *
from Students

You can try to insert a value in your table (Insert into Students ('sid', 'sname', 'GPA', 'dateOfBirth') Values ('NULL', 'joe', '1.7', '200-12-12'); this will solve your problem with the SELECT *
I would also add an auto increment on your sid so you can putt the value of sid to null and it will automatically ALTER TABLE Students MODIFY 'sid' INT(10) NOT NULL AUTO_INCREMENT PRIMARY KEY;

sql how to use select query to get invoke foreign key

i was wondering how do i use the select query to Retrieve all offers of a listing.
Any tips or help to improve my codes is appreciated to! Thank you and have a nice day!
CREATE DATABASE IF NOT EXISTS `assignment_db`;
USE `assignment_db`;
CREATE TABLE USER_LIST(
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
userName VARCHAR(50) NOT NULL,
email varchar(100) NOT NULL,
registeredDate timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
);
create table listing_list(
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
itemName VARCHAR(50) NOT NULL,
itemDescription VARCHAR(254) NOT NULL,
price DECIMAL(4,2) NOT NULL,
fk_poster_id int references USER_LIST(id),
created_at timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
);
create table offer_list(
id int(6) Unsigned auto_increment Primary key,
offer int,
fk_listing_id int references listing_list(id),
fk_offeror_id int references user_list(id),
created_at timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP
);
insert into user_list (userName, email) values ('John','johnnyboi#123.com');
insert into user_list (userName, email) values ('Tom','Tommyboi#123.com');
insert into listing_list (itemName,itemDescription, price) values ( 'Pen', 'A long delicate pen.',' 1.50 ');
insert into listing_list (itemName,itemDescription, price) values ( 'Pencil', 'A long delicate pencil.',' 0.50 ');
insert into offer_list (offer,fk_listing_id,fk_offeror_id) values ('200','2','3');
insert into offer_list (offer,fk_listing_id,fk_offeror_id) values ('200','1','1');

All offer listing for existing user :
select a.*,b.*,c.* from offer_list a
INNER JOIN (listing_list as b)
on a.fk_listing_id=b.Id
INNER JOIN (user_list as c)
on a.fk_offeror_id=c.Id
just all offer listing :
select a.*,b.* from listing_list b
INNER JOIN (offer_list as a)
on a.fk_listing_id=b.Id
just all offer listing 2nd way
select a.*,b.* from offer_list a
INNER JOIN (listing_list as b)
on a.fk_listing_id=b.Id
Check it here , i tested them in this FIDDLE

Auto_increment trigger

I need to auto_increment the primary key in a mysql database using a trigger. Unfortunately, I am not quite sure how to do this. In the sample code I have provided, I need the employee table primary key to auto_increment beginning with an empty table and a starting value of 200. Then, I need each new insert to increment by 1.Thanks for looking and I hope you are able to help me.
CREATE TABLE department (
dept_name VARCHAR(50) NOT NULL Primary Key
);
CREATE TABLE employee (
emp_id INT(6) unsigned Default 0 Not NULL
, last_name VARCHAR(25) NOT NULL
, first_name VARCHAR(40) NOT NULL
, dept_name VARCHAR(50) NOT NULL
, PRIMARY KEY(emp_id, dept_name)
, FOREIGN KEY(dept_name) REFERENCES department (dept_name)
);

There are several things you need to do:
Declare the emp_id column as AUTO_INCREMENT;
Set the value of AUTO_INCREMENT property of the table to 200;
Do not provide any value for column emp_id when you INSERT rows in table employee.
Change the table creation as below:
CREATE TABLE employee (
emp_id INT(6) UNSIGNED NOT NULL AUTO_INCREMENT,
last_name VARCHAR(25) NOT NULL,
first_name VARCHAR(40) NOT NULL,
dept_name varchar(50) NOT NULL
PRIMARY KEY(emp_id),
FOREIGN KEY(dept_name) REFERENCES department_tbl(dept_name)
) AUTO_INCREMENT=200;
If the table has an AUTO_INCREMENT column then it must be the PRIMARY KEY of the table. I removed dept_name from the definition of the PK above. I also removed the default value 0 from the emp_id column. It's default value is generated by MySQL using the AUTO_INCREMENT policy.
When you INSERT a new record into the employee table all you have to do is to not provide any value for the emp_id column:
INSERT INTO employee (last_name, first_name, dept_name)
VALUES ('Doe', 'John', 'accounting');
Then use the LAST_INSERT_ID() MySQL function to retrieve the value of the emp_id generated on insertion.
The language or the library you use to develop the client application probably has a function that wraps LAST_INSERT_ID() and returns its value.

insert query is not working for the row which has a foreign key

I am trying to learn foreign key constraint so far i have been able to create foreign keys in mysql
Here is my create table query for three tables:
create table customer(
CustId int(100) not null AUTO_INCREMENT primary key,
FirstName varchar(300) default null,
LastName varchar(300) default null,
Gender varchar(200) default null,
Category varchar(200) default null,
DateOfBirth varchar(200) default null,
Age int(3)default null
);
create table address(
Address_Id int(100) not null AUTO_INCREMENT primary key,
Address varchar(1000) default null,
Country varchar(500) default null,
State varchar (500) default null,
city varchar(500)default null,
PinCode int(10)default null,
CustId int(100) not null,
foreign key(CustId) references customer(CustId)
);
create table contact(
Contact_Id int(100) not null AUTO_INCREMENT primary key,
EmailId varchar(500)default null,
ContactNo varchar(20) default null,
MobileNo varchar(20) default null,
CustId int(100) not null,
Address_Id int(100) not null,
foreign key(CustId) references customer(CustId),
foreign key(Address_Id) references address(Address_Id)
);
K now i got it till here :
START TRANSACTION;
SET #lid := null;
insert into customer (FirstName,LastName,Gender,Category,DateOfBirth,Age)values('Ashok','sharma','Male','Affiliate','1988-04-17','26');
SELECT LAST_INSERT_ID() INTO #lid;
insert into address(CustId, Address,Country,State,city,Pincode)values (#lid, 'No.1645','India','Karnataka','Bangalore','560060');
COMMIT;
Using transaction and commit was the solution but how to do it for contact table where i have too foreign keys. And i need to get two auto incremented values.
Please guide me on this as well.

You do this in multiple statements:
START TRANSACTION;
SET #lid := null;
insert into customer (FirstName,LastName,Gender,Category,DateOfBirth,Age)values('Ashok','sharma','Male','Affiliate','1988-04-17','26');
SELECT LAST_INSERT_ID() INTO #lid;
insert into address(CustId, Address,Country,State,city,Pincode)values (#lid, 'No.1645','India','Karnataka','Bangalore','560060');
COMMIT;
For MySQL 5.1.12 and later, with no argument, LAST_INSERT_ID() returns a 64-bit value representing the first automatically generated value successfully inserted for an AUTO_INCREMENT column as a result of the most recently executed INSERT statement.
This is session bound, so don't worry, that another session messes up your last_insert_id or something. Read more about it here.
And you better put it all in a transaction like I did. This makes sure, that all statements succeed or none, not just parts of them. You have to use InnoDB for it though. MyISAM does not support this. Or you live with the risk :) But since you use foreign keys I assume you use InnoDB, just wanted to mention it for completeness.
The variable I used can of course be replaced with a PHP variable. Or you do it like this:
START TRANSACTION;
insert into customer (FirstName,LastName,Gender,Category,DateOfBirth,Age)values('Ashok','sharma','Male','Affiliate','1988-04-17','26');
SELECT LAST_INSERT_ID() INTO #lid;
insert into address(CustId, Address,Country,State,city,Pincode)
SELECT #lid, 'No.1645','India','Karnataka','Bangalore','560060';
COMMIT;
EDIT:
START TRANSACTION;
SET #lid_c := null;
SET #lid_a := null;
insert into customer (FirstName,LastName,Gender,Category,DateOfBirth,Age)values('Ashok','sharma','Male','Affiliate','1988-04-17','26');
SELECT LAST_INSERT_ID() INTO #lid_c;
insert into address(CustId, Address,Country,State,city,Pincode)values (#lid, 'No.1645','India','Karnataka','Bangalore','560060');
SELECT LAST_INSERT_ID() INTO #lid_a;
INSERT INTO contact (CustId, Address_Id, another_column) VALUES
(#lid_c, #lid_a, 'another_value');
COMMIT;

Aggregate Query depending on several tables

I want to create a database with information of employees, their jobs, salaries and projects
I want to keep information of the cost of a project (real value of project and the days a employee invested)
For employee and project each Employee has one role on the Project through the PK constraint, and allows for the addition of a new role type ("Tertiary" perhaps) in the future.
CREATE TABLE Employee(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Sex CHAR(1) NOT NULL,
Address VARCHAR(80) NOT NULL,
Security VARCHAR(15) NOT NULL,
DeptID INTEGER NOT NULL,
JobID INTEGER NOT NULL
);
CREATE TABLE Departments (
DeptID INTEGER NOT NULL PRIMARY KEY,
DeptName VARCHAR(30) NOT NULL
);
CREATE TABLE Jobs (
JobID INTEGER NOT NULL PRIMARY KEY,
JobName VARCHAR(30) NOT NULL,
JobSalary DOUBLE(15,3) NOT NULL default '0.000',
JobSalaryperDay DOUBLE(15,3) NOT NULL default '0.000',
DeptID INTEGER NOT NULL
);
CREATE TABLE Project(
ProjectID INTEGER NOT NULL PRIMARY KEY,
ProjectDesc VARCHAR(200) NOT NULL,
StartDate DATE NOT NULL,
EndDate DATE NOT NULL,
DaysOfWork INTEGER NOT NULL,
NoEmployees INTEGER NOT NULL,
EstimatedCost DOUBLE(15,3) NOT NULL default '0.000',
RealCost DOUBLE(15,3) NOT NULL default '0.000'
);
CREATE TABLE `Project-Employee`(
ProjectID INTEGER NOT NULL,
EmployeeID INTEGER NOT NULL,
Note VARCHAR(200),
DaysWork INTEGER NOT NULL,
CONSTRAINT fk_ProjectID FOREIGN KEY (ProjectID) REFERENCES Project(ProjectID),
CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES Employee(EmployeeID)
);
INSERT INTO `Departments` VALUES (1, 'Outsourcing');
INSERT INTO `Departments` VALUES (2, 'Technician');
INSERT INTO `Departments` VALUES (3, 'Administrative');
INSERT INTO `Jobs` VALUES (1, 'welder' ,500.550,16.7 ,2);
INSERT INTO `Jobs` VALUES (2, 'turner' ,500.100,16.67,2);
INSERT INTO `Jobs` VALUES (3, 'assistant' ,650.100,21.67,2);
INSERT INTO `Jobs` VALUES (4, 'supervisor',800.909,26.70,3);
INSERT INTO `Jobs` VALUES (5, 'manager' ,920.345,30.68,3);
INSERT INTO `Jobs` VALUES (6, 'counter' ,520.324,17.35,1);
INSERT INTO `Employee` VALUES (10, 'Joe', 'M', 'Anywhere', '927318344', 1, 3);
INSERT INTO `Employee` VALUES (20, 'Moe', 'M', 'Anywhere', '827318322', 2, 3);
INSERT INTO `Employee` VALUES (30, 'Jack', 'M', 'Anywhere', '927418343', 3, 4);
INSERT INTO `Employee` VALUES (40, 'Marge','F', 'Evererre', '127347645', 1, 6);
INSERT INTO `Employee` VALUES (50, 'Greg' ,'M', 'Portland', '134547633', 3, 5);
INSERT INTO `Project` VALUES (1, 'The very first', '2008-7-04' , '2008-7-24' , 20, 5, 3000.50, 2500.00);
INSERT INTO `Project` VALUES (2, 'Second one pro', '2008-8-01' , '2008-8-30' , 30, 5, 6000.40, 6100.40);
INSERT INTO `Project-Employee` VALUES (1, 10, 'Worked all days' , 20);
INSERT INTO `Project-Employee` VALUES (1, 20, 'Worked just in defs', 11);
INSERT INTO `Project-Employee` VALUES (1, 30, 'Worked just in defs', 17);
INSERT INTO `Project-Employee` VALUES (1, 40, 'Contability ' , 8);
INSERT INTO `Project-Employee` VALUES (1, 50, 'Managed the project', 8);
So to get the total amount of the cost of a project and have it for future Work quote I would just sum the working days of each job for each employee in an aggregate query.
What would be the query to sum all working days knowing the employees involved in a particular project to know the cost generated for their work, Is it possible to know this with this design?
So lets suppose I know that in project 1, 5 employees were involved, and I know by other table "jobs" the salary I would pay each one of them per day
I am doing some queries here with sqlfiddle
UPDATE
CREATE TABLE `Sexes` (
Sex char(1) primary key
);
INSERT INTO Sexes values ('M');
INSERT INTO Sexes values ('F');
CREATE TABLE `Employee`(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(130) NOT NULL,
Sex CHAR(1) NOT NULL,
Address VARCHAR(380) NOT NULL,
Security VARCHAR(15) NOT NULL,
FOREIGN KEY (Sex) references Sexes (Sex),
CONSTRAINT `uc_EmployeeInfo` UNIQUE (`EmployeeID`,`Name`,`Security`)
);
CREATE TABLE `Department` (
DeptID INTEGER NOT NULL PRIMARY KEY,
DeptName VARCHAR(30) NOT NULL,
CONSTRAINT `uc_DeptName` UNIQUE (`DeptID`,`DeptName`)
);
CREATE TABLE `Dept-Employee`(
EmployeeID INTEGER NOT NULL,
DeptID INTEGER NOT NULL,
CONSTRAINT fk_DeptID FOREIGN KEY (DeptID) REFERENCES `Department`(DeptID),
CONSTRAINT fk_EmployeeID FOREIGN KEY (EmployeeID) REFERENCES `Employee`(EmployeeID)
);
CREATE TABLE `Dept-Manager`(
EmployeeID INTEGER NOT NULL,
DeptID INTEGER NOT NULL,
CONSTRAINT fk_DeptIDs FOREIGN KEY (DeptID) REFERENCES `Department`(DeptID),
CONSTRAINT fk_EmployeeIDs FOREIGN KEY (EmployeeID) REFERENCES `Employee`(EmployeeID)
);
CREATE TABLE `Jobs` (
JobID INTEGER NOT NULL PRIMARY KEY,
JobName VARCHAR(30) NOT NULL,
JobSalary DECIMAL(7,3) NOT NULL default '0000.000',
JobSalaryperDay DECIMAL(7,3) NOT NULL default '0000.000',
CONSTRAINT `uc_jobs` UNIQUE (`JobID`,`JobName`)
);
CREATE TABLE `Jobs-Employee`(
EmployeeID INTEGER NOT NULL,
JobID INTEGER NOT NULL,
CONSTRAINT fk_JobIDs FOREIGN KEY (JobID) REFERENCES `Jobs`(JobID),
CONSTRAINT fk_EmployeeIDss FOREIGN KEY (EmployeeID) REFERENCES `Employee`(EmployeeID)
);
CREATE TABLE `Project`(
ProjectID INTEGER NOT NULL PRIMARY KEY,
ProjectName VARCHAR(200) NOT NULL,
StartDate DATE NOT NULL,
DaysOfWork INTEGER NOT NULL,
NoEmployees INTEGER NOT NULL,
EstimatedCost DECIMAL(9,3) NOT NULL default '000000.000',
RealCost DECIMAL(9,3) NOT NULL default '000000.000',
CONSTRAINT `uc_project` UNIQUE (`ProjectID`,`ProjectName`)
);
CREATE TABLE `Project-Employee`(
ProjectID INTEGER NOT NULL,
EmployeeID INTEGER NOT NULL,
Note VARCHAR(200),
DaysWork INTEGER NOT NULL,
CONSTRAINT fk_ProjectIDsss FOREIGN KEY (ProjectID) REFERENCES `Project`(ProjectID),
CONSTRAINT fk_EmployeeIDsss FOREIGN KEY (EmployeeID) REFERENCES `Employee`(EmployeeID)
);
INSERT INTO `Department` VALUES (1, 'Outsourcing');
INSERT INTO `Department` VALUES (2, 'Technician');
INSERT INTO `Department` VALUES (3, 'Administrative');
INSERT INTO `Jobs` VALUES (1, 'welder' ,500.550, 16.7 );
INSERT INTO `Jobs` VALUES (2, 'turner' ,500.100, 16.67);
INSERT INTO `Jobs` VALUES (3, 'assistant' ,650.100, 21.67);
INSERT INTO `Jobs` VALUES (4, 'supervisor',800.909, 26.70);
INSERT INTO `Jobs` VALUES (5, 'manager' ,920.345, 30.68);
INSERT INTO `Jobs` VALUES (6, 'counter' ,520.324, 17.35);
INSERT INTO `Employee` VALUES (10, 'Joe', 'M', 'Joewhere', '927318344');
INSERT INTO `Employee` VALUES (20, 'Moe', 'M', 'Moewhere', '827318322');
INSERT INTO `Employee` VALUES (30, 'Jack', 'M', 'Jaswhere', '927418343');
INSERT INTO `Employee` VALUES (40, 'Marge','F', 'Evererre', '127347645');
INSERT INTO `Employee` VALUES (50, 'Greg' ,'M', 'Portland', '134547633');
INSERT INTO `Dept-Employee` VALUES (10,1);
INSERT INTO `Dept-Employee` VALUES (20,2);
INSERT INTO `Dept-Employee` VALUES (30,3);
INSERT INTO `Dept-Employee` VALUES (40,1);
INSERT INTO `Dept-Employee` VALUES (50,3);
INSERT INTO `Jobs-Employee` VALUES (10,3);
INSERT INTO `Jobs-Employee` VALUES (20,3);
INSERT INTO `Jobs-Employee` VALUES (30,4);
INSERT INTO `Jobs-Employee` VALUES (40,6);
INSERT INTO `Jobs-Employee` VALUES (50,5);
INSERT INTO `Project` VALUES (1, 'The very first', '2008-7-04' , 20, 5, 3000.50, 2500.00);
INSERT INTO `Project` VALUES (2, 'Second one pro', '2008-8-01' , 30, 5, 6000.40, 6100.40);
INSERT INTO `Project-Employee` VALUES (1, 10, 'Worked all days' , 20);
INSERT INTO `Project-Employee` VALUES (1, 20, 'Worked just in defs', 11);
INSERT INTO `Project-Employee` VALUES (1, 30, 'Worked just in defs', 17);
INSERT INTO `Project-Employee` VALUES (1, 40, 'Contability ' , 8);
INSERT INTO `Project-Employee` VALUES (1, 50, 'Managed the project', 8);
To the new structure I did this
CREATE VIEW `Emp-Job` as
SELECT e.*,j.jobID
FROM Employee e,`Jobs-Employee` j
WHERE e.EmployeeID = j.EmployeeID;
CREATE VIEW `employee_pay` as
select e.*, j.jobname, j.jobsalary, j.jobsalaryperday
from `Emp-Job` e
inner join `Jobs` j
on e.JobID = j.JobID;
create view project_pay as
select pe.projectid, pe.employeeid, pe.dayswork,
e.jobsalaryperday, (e.jobsalaryperday * dayswork) as total_salary
from `Project-Employee` pe
inner join `employee_pay` e
on e.employeeid = pe.employeeid

The data at the end of your question doesn't seem to match the data in your INSERT statements.
Have you ever heard of "divide and conquer"? This is a good time to use it. Here's what I'd do.
create view employee_pay as
select e.*, j.jobname, j.jobsalary, j.jobsalaryperday
from employee e
inner join jobs j on e.jobid = j.jobid
create view project_pay as
select pe.projectid, pe.employeeid, pe.dayswork,
e.jobsalaryperday, (e.jobsalaryperday * dayswork) as total_salary
from project_employee pe
inner join employee_pay e
on e.employeeid = pe.employeeid
I'd do that, because I expect those views to be generally useful. (Especially for debugging.) Having created those views, the total for a project is dead simple.
select projectid, sum(total_salary) as total_salaries
from project_pay
group by projectid
projectid total_salaries
--
1 1509.91
You really don't want to use DOUBLE for money. Use DECIMAL instead.
Use this query to sort out why my sum doesn't match yours.
select p.*, e.name
from project_pay p
inner join employee e on e.employeeid = p.employeeid;
projectid employeeid dayswork jobsalaryperday total_salary name
1 10 20 21.67 433.4 Joe
1 20 11 21.67 238.37 Moe
1 30 17 26.7 453.9 Jack
1 40 8 17.35 138.8 Marge
1 50 8 30.68 245.44 Greg
Anti-patterns
Broken identity
Whenever you see a table like this one
CREATE TABLE Departments (
DeptID INTEGER NOT NULL PRIMARY KEY,
DeptName VARCHAR(30) NOT NULL
);
you should assume its structure is wrong, and dig deeper. (It's presumed guilty until proven innocent.) The anti-pattern you look for
integer as an artificial primary key, along with
no other unique constraints.
A table like this allows the real data to be duplicated, eliminating the usefulness of an artificial key.
DeptID DeptName
--
1 Wibble
2 Wibble
...
175 Wibble
A table like this will allow multiple foreign key references, too. That means some of the foreign keys might reference Wibble (DeptID = 1), some might reference Wibble (DeptID = 175), and so on.
To fix that, add a UNIQUE constraint on DeptName.
Missing foreign key references
Whenever you see a table like this one
CREATE TABLE Employee(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
...
DeptID INTEGER NOT NULL,
JobID INTEGER NOT NULL
);
you should assume its structure is wrong, and dig deeper. (Again, it's presumed guilty until proven innocent.) The anti-pattern you look for
ID numbers from other tables, along with
no foreign key constraints referencing those tables.
To fix that, add foreign key constraints for DeptID and JobID. On MySQL, make sure you're using the INNODB engine, too. (As of MySQL 5.6, MyISAM still won't enforce foreign key constraints, but it won't give you an error or warning if you write them. They're parsed and ignored.)
If you come to MySQL from another dbms, you'll be surprised to find that MySQL doesn't support inline foreign key reference syntax. That means you can't write this.
DeptID integer not null references Departments (DeptID)
Instead, you have to write a separate foreign key clause in the CREATE TABLE statement. (Or use a separate ALTER TABLE statement to declare the FK reference.)
DeptID integer not null,
foreign key (DeptID) references Departments (DeptID)
Search this page for "inline ref", but read the whole thing.
Missing CHECK() constraints
MySQL doesn't enforce CHECK() constraints, so for columns that beg for a CHECK() constraint, you need a table and a foreign key reference. When you see a structure like this
CREATE TABLE Employee(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Sex CHAR(1) NOT NULL,
the column "Sex" begs for a CHECK() constraint.
CREATE TABLE Employee(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Sex CHAR(1) NOT NULL CHECK( Sex IN ('M', 'F')),
But MySQL doesn't enforce CHECK() constraints, so you need another table and a foreign key reference.
create table sexes (
sex char(1) primary key
);
insert into sexes values ('M');
insert into sexes values ('F');
CREATE TABLE Employee(
EmployeeID INTEGER NOT NULL PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Sex CHAR(1) NOT NULL,
...
foreign key (Sex) references Sexes (Sex)
I'd consider CHECK() constraints for most of these columns. Some can be implemented as tables with foreign key references.
Employee.Security
Jobs.JobSalary
Jobs.JobSalaryperDay
Project.DaysOfWork
Project.NoEmployees
Project.EstimatedCost
Project.RealCost
Project_Employee.DaysWork
Using floating-point data types for money
Don't do that. Floating-point numbers are useful approximations, but they're still approximations. Use DECIMAL instead.