WGU c170 The Most Important SQL Commands.docx

WGU c170 The Most Important
SQL Commands(SQL study guide)
Course

WGU c170

1. CREATE DATABASE
Creates a new database.

CREATE DATABASE SchoolDB;



2. USE DATABASE
Selects the database you want to work with.

USE SchoolDB;



3. CREATE TABLE
Creates a new table.

CREATE TABLE Student (
StudentID INT PRIMARY KEY,
FirstName VARCHAR(50),
LastName VARCHAR(50),
Email VARCHAR(100)
);



4. PRIMARY KEY
Uniquely identifies each row.

CREATE TABLE Student (
StudentID INT PRIMARY KEY,
FirstName VARCHAR(50),
LastName VARCHAR(50)
);

Remember: A primary key must uniquely identify a record and cannot be NULL.

, 5. FOREIGN KEY
Creates a relationship between tables.

CREATE TABLE Enrollment (
EnrollmentID INT PRIMARY KEY,
StudentID INT,
CourseID INT,
FOREIGN KEY (StudentID) REFERENCES Student(StudentID),
FOREIGN KEY (CourseID) REFERENCES Course(CourseID)
);

Remember:

PRIMARY KEY = identifies the row
FOREIGN KEY = connects tables



6. INSERT INTO
Adds records to a table.

INSERT INTO Student (StudentID, FirstName, LastName, Email)
VALUES (1, 'John', 'Smith', '');

Multiple rows:

INSERT INTO Student (StudentID, FirstName, LastName, Email)
VALUES
(2, 'Mary', 'Jones', ''),
(3, 'David', 'Brown', '');



7. SELECT
Retrieves data.

SELECT *
FROM Student;

Select specific columns:

SELECT FirstName, LastName
FROM Student;