CREATE TABLE Users(
ID INT NOT NULL,
NAME VARCHAR(20) NOT NULL,
AGE INT NOT NULL,
PRIMARY KEY(ID)
);
CREATE TABLE Orders(
OID INT NOT NULL,
DATE DATETIME,
AMOUNT INT,
USER_ID INT,
FOREIGN KEY (USER_ID) references Users(ID),
-- or USER_ID INT references Users(ID),
PRIMARY KEY(OID)
);-- Add a Primary Key to an existing table
ALTER TABLE Users ADD PRIMARY KEY (ID);
-- Add a Foreign Key to an existing table
ALTER TABLE Orders
ADD FOREIGN KEY (USER_ID) REFERENCES Users(ID);- DDL - Data Definition Language - CREATE, ALTER, DROP
- DML - Data Manipulation Language - SELECT, INSERT, UPDATE, DELETE
- DCL - Data Control Language - GRANT, REVOKE
- TCL - Transaction Control Language - SAVEPOINT, ROLLBACK, COMMIT
SELECT column1, column2, columnN FROM table_name;
SELECT * FROM table_name;
SELECT * -- SELECT Users.age
FROM table_name -- FROM Users
WHERE [condition]; -- WHERE name = 'John'Note
The WHERE clause is used in SELECT, INSERT and UPDATE statements
INSERT INTO table_name (column1, column2,...columnN)
VALUES (value1, value2,...valueN);- Used to combine records from two or more tables in a database.
- A means for combining fields from two tables by using values common to each.
- Different Types of Joins
- INNER JOIN
- LEFT JOIN
- RIGHT JOIN
- FULL JOIN
SELECT ID, NAME, AGE, AMOUNT
FROM Users
INNER JOIN Orders
ON Users.ID = Orders.USER_ID;