SQL Tutorial course teaches you how to use basics of SQL language.
It is a sql tutorial for beginners.

1. Introduction to SQL

First of all you need to create an sql table in a SQL Server database.
Uses the command create table.

CREATE TABLE tutorials
(
id int,
name varchar(150),
duration int,
price int
);

CREATE TABLE tutorial_orders
(
order_id int,
tutorial_id int,
order_date date
);

Insert rows into a sql table.

INSERT INTO tutorials(id, name, duration, price)
VALUES (1, 'SQL tutorial', 2, 200);
INSERT INTO tutorials(id, name, duration, price)
VALUES (2, 'T-SQL tutorial', 5, 300);
INSERT INTO tutorials(id, name, duration, price)
VALUES (3, 'Learn ASP', 5, 400);
INSERT INTO tutorials(id, name, duration, price)
VALUES (4, 'PHP tutorial', 3, 200);
INSERT INTO tutorials(id, name, duration, price)
VALUES (5, 'Learn HTML', 2, 100);

INSERT INTO tutorial_orders(order_id, tutorial_id, order_date)
VALUES (1, 3, getdate());
INSERT INTO tutorial_orders(order_id, tutorial_id, order_date)
VALUES (2, 1, getdate());
INSERT INTO tutorial_orders(order_id, tutorial_id, order_date)
VALUES (3, 6, getdate());

Select information from a table.

select * from tutorials;
select * from tutorials where id=3;
select * from tutorials where duration=2;
select * from tutorials where price>200;
select * from tutorials where name like '%SQL%';

Modify the value of the columns in a table.

update tutorials set price=price+20;
update tutorials set name='Learn Microsoft ASP' where id=3;
update tutorials set duration=1 where duration=2;
update tutorials set price=price+100 where price>200;
update tutorials set duration=4 where name like '%SQL%';

Delete rows from a table.

delete from tutorials;
delete from tutorials where id=3;
delete from tutorials where duration=2;
delete from tutorials where price>200;
delete from tutorials where name like '%SQL%';




2. Extract and Filter data

DISTINCT – eliminate duplicate rows in a select.
Return distinct values from one or multiple columns of a table.

select distinct duration from tutorials;

WHERE – is the search condition for the rows returned by the select statement.

select * from tutorials where id=3;

AND – compare two expressions and return true if both expressions are true.

select * from tutorials where duration=2 and price=100;

OR – compare two expressions and return true if at least one expression is true.

select * from tutorials where price=700 or duration=5;

BETWEEN – return rows if the value is within the range of comparisons.

select * from tutorials where price between 250 and 700;

LIKE – return rows if a character string matches a pattern.

select * from tutorials where name like '%SQL%';
select * from tutorials where name like 'Le%';
select * from tutorials where name like '%SQL';

IN – return rows if a value is equal to one value in a list or a subquery.

select * from tutorials where duration in (4,5);




3. Group data, Limit and Sorting rows

GROUP BY - divides the query result into groups of rows.
The GROUP BY is used when an aggregate function exists in the select statement.

select price, count(price) from tutorials group by price;

HAVING - specifies a search condition for a group or an aggregate.

select price, count(price)
from tutorials
group by price
having count(price)>1;

TOP – is used to limit the number of rows in a select query.

select TOP 1 * from tutorials;
select top(2) * from tutorials order by price desc;
select TOP 50 PERCENT * from tutorials;

ORDER BY – is used to sort rows returned in an select statement.

select * from tutorials order by price DESC, id ASC;




3. Table Joins

INNER JOIN - returns only the rows for which there is an match in both tables.

select * from tutorials t
inner join tutorial_orders o
on t.id = o.tutorial_id ;

LEFT JOIN - returns all rows from the left table, even if there are no matches with the right table.

select * from tutorials t
left join tutorial_orders o
on t.id = o.tutorial_id ;

RIGHT JOIN - returns all rows from the right table, even if there are no matches with the left table.

select * from tutorial_orders o
right join tutorials t
on o.tutorial_id = t.id;

SELF JOIN - is used to join a table to itself.

select * from tutorials t1, tutorials t2 where t1.id=t2.id;




4. Subquery

IN – check if a value is equal to one value in a subquery.

select * from tutorials t
where t.id IN (select o.tutorial_id from tutorial_orders o);

ANY – compare if any value is equal to one value in a subquery.

select * from tutorials t
where t.id = ANY (select o.tutorial_id from tutorial_orders o);

ALL – compare if all values is equal to all values in a subquery.

select * from tutorials t
where t.id = ALL (select o.tutorial_id from tutorial_orders o);

SOME – match at least one row in the subquery.

select * from tutorials t
where t.id = SOME (select o.tutorial_id from tutorial_orders o);

EXISTS – return rows if a subquery contains any rows.

select * from tutorials t
where EXISTS (select * from tutorial_orders o where o.tutorial_id=t.id);

NOT EXISTS – return rows if a subquery not contains any rows.

select * from tutorials t
where NOT EXISTS (select * from tutorial_orders o where o.tutorial_id=t.id);




5. Aggregate functions

AVG - returns the average value of an expression.

select avg(price) from tutorials;
select avg(price) from tutorials where duration=5;

SUM - returns the sum of all values of an expression.

select sum(price) from tutorials;
select sum(price) from tutorials where duration=5;

MAX - returns the max value of an expression.

select max(price) from tutorials;
select max(price) from tutorials where duration=2;

MIN - returns the min value of an expression.

select min(price) from tutorials;
select min(price) from tutorials where duration=5;

COUNT - returns the number of rows returned by a select statement.

select count(*) from tutorials;
select count(*) from tutorials where price > 200;
select price, count(*)
from tutorials
group by price
having count(*)>1;