Important MySQL short notes PDF for beginners 2021

INSERT INTO students(id,name,age,phone) VALUES(6,'Noman',16,'016349823xx') 

insert into students(id,name,age,phone) values(6,'Noman',16,'016349823xx')

INSERT INTO students(id,name,age,phone) VALUES(6,'Noman',16,'016349823xx')

INSERT INTO students(id,name,age,phone) VALUES(6,'Noman',16,'016348823xx');
INSERT INTO students(id,name,age,phone) VALUES(7,'Arafat',20,'016339823xx');
INSERT INTO students(id,name,age,phone) VALUES(8,'Kamrul',19,'016345823xx');
INSERT INTO students(id,name,age,phone) VALUES(9,'Monju',17,'014345823xx')

CREATE DATABASE student_db

CREATE TABLE students (
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL,
age INT(6),
phone VARCHAR(30) NOT NULL
)

😍 Learn MoreThe Best way of creating a table in MySQL.

✍ The SQL INSERT statement is used to insert data into the database.
✍ We don't need to use column name when we INSERT data, if Table columns order and given data order are the same and We provide all columns value.
✍ Insert query return true or false. If data INSERT success it will return true, Else it will return false.

INSERT INTO students(id,name,age,phone) VALUES (6,'Noman',16,'016349823xx');

INSERT INTO students VALUES(6,'Noman',16,'016349823xx');

✍ SELECT Statement is used to fetch data from the database.
✍ To Fetch all columns we need to yous * sign. (* = All).
✍ We can also specify which column we want to fetch.

SELECT * FROM students

SELECT name,email,phone FROM students

✍ Where close use to define the condition in SQL statement.
✍ We can fetch data Conditionally.
✍ It works like the "if" condition.

SELECT * FROM students WHERE age > 18

✍ UPDATE Statement used to update record.
✍ When we use update statements we need to use conditions with where close.
✍ If we don’t use where close properly all records will update automatically.
Don't do like this

UPDATE students SET age = 19

UPDATE students SET age = 19 WHERE id = 5

✍ UPDATE Statement used to Delete record.
✍ When we use delete statements we need to use conditions with where clause.
✍ If we don't use the where clause properly all records will delete automatically.
Don't do like this

DELETE FROM students;

DELETE FROM students WHERE id = 5

✍ We can use the LIMIT statement to specify how many records we want to fetch from the table.
✍ Also, we can specify FROM which record fetching will start.

SELECT * FROM students LIMIT 5;

SELECT * FROM students LIMIT 3, 8;

✍ we can use MySQL AND, OR, NOT conditions with WHERE clause like this.

SELECT * FROM students WHERE age > 18 AND age < 21

SELECT * FROM students WHERE age > 18 OR size > 6

SELECT * FROM students WHERE NOT class = 10 

✍ MySQL Aggregate functions are so important topic.
✍ In general, we have five Aggregate functions.

• 📌 1. COUNT()
        ⬆This function will count all rows.
• 📌 2. MAX()
        ⬆This function will return the maximum value from all rows.
• 📌 3. MIN()
        ⬆This function will return the maximum value from all rows.
• 📌 4. AVG()
        ⬆This function will return the average value from all rows.
• 📌 5. SUM()
        ⬆This function will return the summation value from all rows.

😍 Learn MySQL Aggregate functions with example.

✍ To create search features we can use MySQL LIKE statement.
✍ For pattern matching, we need to use MySQL LIKE Statement.
✍ The SQL LIKE statements is so important topic in the database. you can do so many different things using this LIKE statement.
✍ SQL LIKE statement is so important for Interview and EXAM.

SELECT * FROM students WHERE name LIKE "%keyword%"

😍 Learn MySQL LIKE statement with a real-life example.

✍ We use Wildcard Characters with LIKE statements.
✍ MySQL has 2 wildcard Characters percentages and underscores ( % and _ ).
✍ Percentage(%) represents zero or more characters.
✍ Underscores( _ ) represents a single character.

😍 Learn Use of MySQL wildcard characters with an example.

✍ Using MySQL IN operator we can use multiple values in where close condition. It works like this OR operator.
✍ MySQL IN operator works like PHP in_array() function.

SELECT * FROM students WHERE age IN (17,18,19,20);

✍ TO select data FROM a range we can use MySQL BETWEEN operator.
✍ MySQL BETWEEN operator works like >= and <=. That means it includes the condition values.

SELECT * FROM students WHERE age BETWEEN 18 AND 20

✍ TO sort data we can use ORDER BY and ASC(ascending), DSC (descending)keyword.
✍ Using this ODER BY keyword you can nth maximum or nth minimum records easily.

	SELECT * FROM students ORDER BY age ASC
	

	SELECT * FROM students ORDER BY age DSC
	

✍ A NULL value means no value.
✍ NULL value and zero(0) value are not the same.
✍ We can not use conditional operator(<,<,=,!) to check NULL value.
✍ TO check NULL value we need to use IS NULL or IS NOT a NULL statement.

SELECT * FROM students where name IS NOT NULL

✍ Using MySQL Group BY statement we can fetch row BY Group-wise.
✍ Most of the time we use MySQL Group Statement with our Aggregate functions.
✍ We can use multiple column names in the MySQL Group BY Statement.

SELECT count(*) AS total, name, age
FROM students 
GROUP BY name, age;

✍ Technically the MySQL WHERE and HAVING is the same but We can not use WHERE statements with the Aggregate function that’s why we need to use HAVING close.

SELECT COUNT(age) AS Total, Name
FROM Students
GROUP BY age
HAVING COUNT(age) > 17;

✍ MySQL EXISTS Operator used with a subquery.
✍ It returns true or false, if data exists it returns true of not return false.
✍ MySQL EXISTS is so powerful when we need to run complex queries.

✍ Using MySQL Aliases we can create a temporary name of our table and columns.
✍ To create Aliase we need to use MySQL AS Statement.
✍ To run complex query we need to use Aliases.

SELECT SUM(age) AS Total_AGE FROM students;

😍 Learn MySQL Aliases with an example.

✍ To select data based on multiple conditions we can use MySQL CASE statement.
✍ MySQL CASE Statement work like an if-else condition.
✍ MySQL CASE Statement works like a switch case.
✍ MySQL CASE Statement is so useful topic for Interviews.

😍 Learn MySQL Case Statement with an Example.

✍ MySQL joins are used to fetch data FROM multiple tables.
✍ MySQL joins is one of the main topics in relational databases.
✍ MySQL CASE Statement works like a switch case.
✍ In general, there are four types of joins present in MySQL.

• 📌 INNER JOIN
• 📌 LEFT JOIN
• 📌 RIGHT JOIN
• 📌 CROSS JOIN

😍 Must Learn How MySQL JOIN statements work.

✍ In general, the MySQL UNION Statement works like the union of mathematics.
✍ MySQL Union is one of the important topics for interviews and exams.

😍 Must Learn How MySQL Union Statement work?

✍ To create a table based on another table we can use MySQL INSERT INTO SELECT statement.
✍ INSERT INTO SELECT is so important for Interview and EXAM.

😍 Must Learn MySQL INSERT INTO SELECT statement with an example.

✍ Like other programming languages, MySQL has also comment features.
✍ MySQL Comments is so useful and important for exam and interview.
✍ Single line comment -- this is a comment.
✍ Multi-line comment /* this is multi-line comment */.
✍ We can please comments inside the MySQL Query.

SELECT name, phone FROM students; --this is a single-line comment

SELECT name, phone FROM students;
/*
This is 
multi-line comment
*/

SELECT name, /*age,*/ phone FROM students;