Many database engines support auto-incrementing primary keys, and I would like to use this approach in my new DuckDB approach, but I can't figure out how to set it up. For example, in MySQL:
CREATE TABLE Persons (
Personid int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (Personid)
);
create a table:
CREATE TABLE Persons (
Personid integer primary key,
LastName varchar(255) not null,
FirstName varchar(255),
Age integer
);
create a sequence:
CREATE SEQUENCE seq_personid START 1;
Insert some data:
INSERT INTO Persons VALUES (nextval('seq_personid'), 'Doe', 'John', 99);
Related
hi i found an answer here and used the exemple
CREATE TABLE Persons (
Personid int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
but when i enter records, it does not allow duplicates in column lastname?!
i would expect id 3 and "hans" but it makes NULL?! it shouldnt be a problem that there is again name hans in row 3 ...
what do i wrong?
If do you want to do autoincrement on Personid, you should do:
CREATE TABLE Persons (
Personid int AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (Personid) );
And if do you want insert something into:
INSERT INTO Persons (LastName, FirstName, Age int) VALUES (..,..,..)
I hope I've helped.
New to SQL, can't figure out what is wrong in my given code. all it says is:
Incorrect syntax near 'DESCRIBE'. [41,1]
I have tried taking off the semi-colons. I really just don't know what it wants from me.
Here is my code. Anything helps, thank you!
-- Write the query to create the 4 tables below.
CREATE TABLE client (
id INT NOT NULL IDENTITY(1,1),
first_name VARCHAR(255) NOT NULL,
last_name VARCHAR(255) NOT NULL,
dob DATE NOT NULL,
PRIMARY KEY (id),
CONSTRAINT (full_name) UNIQUE (first_name, last_name)
);
CREATE TABLE employee (
id INT NOT NULL IDENTITY(1,1),
first_name VARCHAR(255) NOT NULL,
last_name VARCHAR(255) NOT NULL,
dob DATE NOT NULL,
date_joined DATE NOT NULL,
CONSTRAINT (full_name) UNIQUE (first_name, last_name),
PRIMARY KEY (id)
);
CREATE TABLE project (
id INT NOT NULL IDENTITY(1,1),
cid INT NOT NULL,
name VARCHAR(255) NOT NULL,
notes TEXT,
UNIQUE (name),
FOREIGN KEY (cid) REFERENCES client(id)
);
CREATE TABLE works_on (
eid INT NOT NULL,
pid INT NOT NULL,
start_date DATE NOT NULL,
PRIMARY KEY (eid, pid),
FOREIGN KEY (eid) REFERENCES employee(id),
FOREIGN KEY (pid) REFERENCES project(id)
);
-- Leave the queries below untouched. These are to test your submission correctly.
-- Test that the tables were created
DESCRIBE client;
DESCRIBE employee;
DESCRIBE project;
DESCRIBE works_on;
-- Test that the correct foreign keys were created
SELECT TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME,REFERENCED_TABLE_NAME,REFERENCED_COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_SCHEMA = 'grade';
For MariaDB (and MySQL) the correct syntax for IDENTITY(1,1), is AUTO_INCREMENT, and CONSTRAINT names are not enclosed in (). Any column that is defined as AUTO_INCREMENT must also be declared as a PRIMARY KEY (this is only an issue with the project table). So your CREATE TABLE commands should look like this:
CREATE TABLE client (
id INT NOT NULL AUTO_INCREMENT,
first_name VARCHAR(255) NOT NULL,
last_name VARCHAR(255) NOT NULL,
dob DATE NOT NULL,
PRIMARY KEY (id),
CONSTRAINT full_name UNIQUE (first_name, last_name)
);
CREATE TABLE employee (
id INT NOT NULL AUTO_INCREMENT,
first_name VARCHAR(255) NOT NULL,
last_name VARCHAR(255) NOT NULL,
dob DATE NOT NULL,
date_joined DATE NOT NULL,
CONSTRAINT full_name UNIQUE (first_name, last_name),
PRIMARY KEY (id)
);
CREATE TABLE project (
id INT NOT NULL AUTO_INCREMENT,
cid INT NOT NULL,
name VARCHAR(255) NOT NULL,
notes TEXT,
PRIMARY KEY (id),
UNIQUE (name),
FOREIGN KEY (cid) REFERENCES client(id)
);
CREATE TABLE works_on (
eid INT NOT NULL,
pid INT NOT NULL,
start_date DATE NOT NULL,
PRIMARY KEY (eid, pid),
FOREIGN KEY (eid) REFERENCES employee(id),
FOREIGN KEY (pid) REFERENCES project(id)
);
Demo on dbfiddle
CREATE TABLE Persons
(
ID int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (ID)
);
When I run this code, it is not run successfully.
Syntax for MySQL
CREATE TABLE Persons (
ID int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (ID)
);
Syntax for SQL Server
CREATE TABLE Persons (
ID int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
Syntax for Oracle
CREATE SEQUENCE seq_person
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;
If this is Microsoft SQL Server then change to IDENTITY instead of Auto_Number. If it's Postgres then I believe you want SERIAL as the datatype instead of INT. If this is MySQL then it should work as-is.
What RDBMS are you using?
SQL Error
I'm not sure what I did wrong here
Here is the DDL I used to create my tables
Create Table HomeState (StateAbbreviation char(2) Primary Key,
StateName varchar(25));
Create Table Country (CountryAbbreviation char(2) Primary Key,
CountryName varchar(35));
Create Table Employee (EmployeeID Integer Primary Key NOT NULL,
FirstName varchar(20),
LastName varchar(30),
MI char(1),
HomeAddress varchar(30),
Zip char(5),
DateOfBirth date,
HireDate date,
TerminationDate date,
AnnualSalary number(20,2),
LicenseDate date,
StateAbbreviation char(2),
CountryAbbreviation char(2),
Foreign Key (StateAbbreviation) references HomeState,
Foreign Key (CountryAbbreviation) references Country);
Create Table Truck (VinNumber Integer Primary Key,
Make varchar(25),
Model varchar(30),
Year Integer,
PurchasePrice number(20,2),
LicenseNumber varchar(15));
Create Table EmployeeTruck (EmployeeID Integer,
VinNumber Integer,
Primary Key(EmployeeID,VinNumber),
Foreign Key (EmployeeID) references Employee,
Foreign Key (VinNumber) references Truck);
Create Table Accident (AccidentID Integer Primary Key,
DateOfAccident date,
AccidentDescription varchar(200),
AccidentLocation varchar(100),
EmployeeID Integer,
Foreign Key (EmployeeID) references Employee);
and here is the command i used to try and fill in the employee table
insert into employee
values ('1','brian','kim','j','adfasdf',
'1234','24-nov-1993','24-sep-1993','24-sep-1993',
'1234','24-sep-1993','as','as')
but it always gives me the error i put as the title of this question...
In the table "Employee", you say that Foreign Key (StateAbbreviation) references HomeState, and Foreign Key (CountryAbbreviation) references Country). The values you insert into Employee.HomeState and Employee.CountryAbbreviation have to exist in the tables HomeState and Country before you can insert into Employee.
Insert rows into HomeState and Country before you insert into Employee.
You have other problems, too. Here's an example.
Create Table HomeState (StateAbbreviation char(2) Primary Key,
StateName varchar(25));
insert into HomeState values ('AL', 'Alabama');
insert into HomeState values ('AM', 'Alabama');
insert into HomeState values ('AN', 'Alabama');
All those insert statements succeed. They shouldn't. In this case, StateName is also a candidate key.
Create Table HomeState (
StateAbbreviation char(2) Primary Key,
StateName varchar(25) not null unique
);
Let's take this a little further.
Create Table HomeState (
StateAbbreviation char(2) Primary Key,
StateName varchar(25) not null unique
);
Create Table Country (
CountryAbbreviation char(2) Primary Key,
CountryName varchar(35) not null unique
);
insert into HomeState values ('CA', 'California');
insert into Country values ('AF', 'Afghanistan');
insert into Employee (EmployeeID, StateAbbreviation, CountryAbbreviation)
values (-42, 'CA', 'AF');
The state "California, US" makes sense. The state "California, Afghanistan" doesn't.
An employee having no name doesn't make sense. Declare FirstName, LastName, and HireDate not null.
Bet on this: whatever nonsense your database allows will appear. It's just a matter of time.
For some reason I'm getting an error* in my code. I'm quite new to PostgreSQL, and simply SQL. What is causing this error?
*there is no unique constraint matching given keys for referenced table "tech".
BEGIN;
CREATE TABLE Person (
person_id SERIAL PRIMARY KEY,
firstname VARCHAR(128),
lastname VARCHAR(128),
email_adr VARCHAR(128),
UNIQUE(person_id, email_adr)
);
CREATE TABLE Phone (
person_id INT REFERENCES Person(person_id),
phone_nr INT PRIMARY KEY,
UNIQUE(phone_nr)
);
CREATE TABLE Tech (
tech_id INT REFERENCES Person(person_id),
username VARCHAR(80) PRIMARY KEY,
password VARCHAR(80) NOT NULL,
location Varchar(128),
UNIQUE(username, tech_id)
);
CREATE TABLE Customer (
customer_id INT REFERENCES Persons(person_id),
addresse VARCHAR(255) NOT NULL,
UNIQUE(customer_id)
);
CREATE TABLE Task (
task_id SERIAL PRIMARY KEY,
payment MONEY,
tech INT REFERENCES Tech(tech_id) NOT NULL,
customer INT REFERENCES Customer(customer_id) NOT NULL,
start_date DATE NOT NULL,
end_dato DATE,
UNIQUE(tech, customer, start_date, end_date)
);
COMMIT;
In table Task you trying to reference to table Tech by tech_id. To do that you must add UNIQUE CONSTRAINT to tech_id in Tech.
Right now in table Tech you have UNIQUE(username, tech_id) that means that values in column tech_id could by doubled Ex.
Tech
-------------------------------
tech_id username, ....
------------------------------
1 'John'
2 'Tony'
1 'Nataly'
Acctually the better idea is to set reference by PRIMARY KEY, so in your case username in table Tech.
If you want to leave structure the way present in question, you should just add UNIQUE(tech_id) in column Tech.
What do you think of this code?
BEGIN;
CREATE TABLE Person (
person_id SERIAL PRIMARY KEY,
firstname VARCHAR(128),
lastname VARCHAR(128),
email_adr VARCHAR(128),
UNIQUE(person_id),
UNIQUE(email_adr)
);
CREATE TABLE Phone (
person_id INT,
phone_nr INT PRIMARY KEY,
);
CREATE TABLE Tech (
tech_id INT,
username VARCHAR(80) PRIMARY KEY,
password VARCHAR(80) NOT NULL,
location Varchar(128),
FOREIGN KEY(tech_id) REFERENCES Person(person_id),
UNIQUE(username),
UNIQUE(tech_id)
);
CREATE TABLE Customer (
customer_id INT REFERENCES Persons(person_id),
addresse VARCHAR(255) NOT NULL,
FOREIGN KEY(tech_id) REFERENCES Person(person_id),
UNIQUE(customer_id)
);
CREATE TABLE Task (
task_id SERIAL PRIMARY KEY,
payment MONEY,
tech varchar(80) REFERENCES Tech(username) NOT NULL,
customer INT REFERENCES Customer(customer_id) NOT NULL,
start_date DATE NOT NULL,
end_dato DATE,
UNIQUE(tech, customer, start_date, end_date)
);
COMMIT;