CREATE TABLE emp(
  id INTEGER PRIMARY KEY,
  emp_name TEXT NOT NULL,
  emp_age TEXT NOT NULL,
  emp_salary DOUBLE
);

CREATE TABLE dept(
  id INTEGER PRIMARY KEY,
  dept_name TEXT NOT NULL,
  budget DOUBLE,
  manager_name TEXT,
  manager_id INT
);

CREATE TABLE works(emp_id INTEGER, dept_id INTEGER,pct_time integer, 
foreign key (emp_id) references emp(id), foreign key (dept_id) 
references dept(id));

-- insert
INSERT INTO emp VALUES (1, 'Thomas', 23,2000),(2, 'Anderson',28 , 3000),
(3, 'Karl', 30 ,6000),(4, 'Andrew', 25 ,9000),(5, 'Jack', 22 ,4000),
(6, 'Bruce',32 ,4500);
INSERT INTO dept VALUES (11, 'Hardware',1000000,'Paul',111),
(22, 'Software',2000000 ,'Jaismin',222);
INSERT INTO works VALUES (1,11,60),(1,22,50),(2,11,45),
(3,11,68),(4,22,80),(5,22,95),(6,22,55);

-- fetch 
SELECT * FROM emp;
SELECT * FROM dept;
SELECT * FROM works;

SELECT  e.emp_name,e.emp_age ,e.id FROM  emp e inner join works w on e.id=w.emp_id 
group by e.id
having count(*)>1; --1

select d.manager_name,group_concat(e.emp_name) from works w inner join dept d on d.id=w.dept_id  inner join emp e on e.id=w.emp_id group by manager_name; --2
 
select w.dept_id, COUNT (w.emp_id) FROM works w GROUP BY w.dept_id HAVING   100< ( SELECT SUM (w1.pct_time)
		FROM    works w1 WHERE w1.dept_id = w.dept_id); --3


select distinct (emp_name) from emp e inner join works w
on w.emp_id = e.id inner join dept d 
on d.id=w.dept_id where e.emp_salary <d.budget; --4

select manager_id from dept where budget > 1000000 ; ---5

select manager_name from dept where budget in (select max (budget) from dept);--6

MySQL online editor

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About MySQL

MySQL is a open-source, free and very popular relational database management system which is developed, distributed and supported by Oracle corporation.

Key Features:

  • Open-source relational database management systems.
  • Reliable, very fast and easy to use database server.
  • Works on client-server model.
  • Highly Secure and Scalable
  • High Performance
  • High productivity as it uses stored procedures, triggers, views to write a highly productive code.
  • Supports large databases efficiently.
  • Supports many operating systems like Linux*,CentOS*, Solaris*,Ubuntu*,Windows*, MacOS*,FreeBSD* and others.

Syntax help

Commands

1. CREATE

CREATE TABLE table_name (
                column1 datatype,
                column2 datatype,
                ....);

Example

CREATE TABLE EMPLOYEE (
  empId INTEGER PRIMARY KEY,
  name TEXT NOT NULL,
  dept TEXT NOT NULL
);

2. ALTER

ALTER TABLE Table_name ADD column_name datatype;

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Dave', 'Sales');

3. TRUNCATE

TRUNCATE table table_name;

4. DROP

DROP TABLE table_name;

5. RENAME

RENAME TABLE table_name1 to new_table_name1;

6. COMMENT

Single-Line Comments:

 --Line1;

Multi-Line comments:

   /* Line1,
   Line2 */

DML Commands

1. INSERT

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

Note: Column names are optional.

Example

INSERT INTO EMPLOYEE VALUES (0001, 'Ava', 'Sales');

2. SELECT

SELECT column1, column2, ...
FROM table_name
[where condition];

Example

SELECT * FROM EMPLOYEE where dept ='sales';

3. UPDATE

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

Example

UPDATE EMPLOYEE SET dept = 'Sales' WHERE empId='0001';

4. DELETE

DELETE FROM table_name where condition;

Example

DELETE from EMPLOYEE where empId='0001';

Indexes

1. CREATE INDEX

  CREATE INDEX index_name on table_name(column_name);
  • To Create Unique index:
  CREATE UNIQUE INDEX index_name on table_name(column_name);

2. DROP INDEX

DROP INDEX index_name ON table_name;

Views

1. Create a View

Creating a View:
CREATE VIEW View_name AS 
Query;

2. How to call view

SELECT * FROM View_name;

3. Altering a View

ALTER View View_name AS 
Query;

4. Deleting a View

DROP VIEW View_name;

Triggers

1. Create a Trigger

CREATE TRIGGER trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW [trigger_order] trigger_body
/* where
trigger_time: { BEFORE | AFTER }
trigger_event: { INSERT | UPDATE | DELETE }
trigger_order: { FOLLOWS | PRECEDES } */

2. Drop a Trigger

DROP TRIGGER [IF EXISTS] trigger_name;

Stored Procedures

1. Create a Stored Procedure

CREATE PROCEDURE sp_name(p1 datatype)
BEGIN
/*Stored procedure code*/
END;

2. How to call Stored procedure

CALL sp_name;

3. How to delete stored procedure

DROP PROCEDURE sp_name;

Joins

1. INNER JOIN

SELECT * FROM TABLE1 INNER JOIN TABLE2 where condition;

2. LEFT JOIN

SELECT * FROM TABLE1 LEFT JOIN TABLE2 ON condition;

3. RIGHT JOIN

SELECT * FROM TABLE1 RIGHT JOIN TABLE2 ON condition;

4. CROSS JOIN

SELECT select_list from TABLE1 CROSS JOIN TABLE2;