1. Databases
and
SQL – Structured Query
Language

2. Совокупность данных из набора
двумерных таблиц:

3. - Огромные объемы данных
- Огромное число пользователей
- Гибкая, не ограниченная схемой
структура БД.
- NoSQL используют: Facebook, eBay

4. Помогает избавиться от избыточности в
отношениях и оптимизировать работу БД

5. Ключ – это набор столбцов таблицы,
которые уникально определяют
строку.
Суррогатный ключ – уникальный ключ
искусственного происхождения
(Например ID или просто порядковый
номер)

6. Нормализация – подразумевает приведение
БД к одной из НФ
Всего их 6
Обычно используются первых 3

7. Каждая строка должна хранить одно-
единственное значение и не являться
списком. Атрибут должен быть атомарным.

8. - Устранение избыточности данных
- Использование атомарных(не составных)
ключей

9. Факты, хранимые в таблицах должны
зависеть только от ключа

10. Команды состоят из:
 - имен операций и функций
 - имен таблиц и их стобцов
 - зарезервированных ключевых слов и
спец.символов
 - логических и арифметических выражений.

11. SELECT CustomerName, City
FROM Customers;
or
SELECT * FROM Customers;

12. DISTINCT - In a table, a column may contain
many duplicate values.
The DISTINCT keyword can be used to return
only distinct (different) values.
SELECT DISTINCT City
FROM Customers;

13. The WHERE clause is used to extract only those
records that fulfill a specified criterion
SELECT *
FROM Customers
WHERE Country='Mexico';

14.  The AND operator displays a record if both the
first condition AND the second are true.
 The OR operator displays a record if either the
first condition OR the second condition is true.
SELECT * FROM Customers
WHERE Country='Germany'
AND City='Berlin';

15. SELECT * FROM Customers
WHERE City='Berlin'
OR City='München';
SELECT * FROM Customers
WHERE Country='Germany'
AND (City='Berlin' OR City='München');

16. The ORDER BY keyword is used to sort the
result-set by one or more columns, it’s
ascending by default. If you want descending
order use DESC keyword.
SELECT * FROM Customers
ORDER BY Country DESC;

17. The INSERT INTO statement is used to insert
new records in a table.
INSERT INTO Customers
(CustomerName, ContactName,
Address, City, PostalCode, Country)
VALUES ('Cardinal','Tom B.
Erichsen','Skagen
21','Stavanger','4006','Norway');

18. The UPDATE statement is used to update
existing records in a table
UPDATE Customers
SET ContactName='Alfred Schmidt', City='Hamburg'
WHERE CustomerName='Alfreds Futterkiste';
Be careful when updating records. If we had
omitted the WHERE clause all rows would be
updated!

19. The DELETE statement is used to delete rows in a
table:
DELETE FROM Customers
WHERE CustomerName='Alfreds Fkiste';
Or
DELETE FROM Customers;
All rows will be deleted!

20. The LIKE operator is used to search for a
specified pattern in a column:
SELECT * FROM Customers
WHERE City LIKE 's%';
Or
SELECT * FROM Customers
WHERE Country(NOT) LIKE '%land%';
All customers with a Country containing the
pattern "land"

21. SQL wildcard characters are used with the SQL LIKE
operator:
%-Заменяет любое кол-во симоволов
_ - Заменяет один символ
[abc] – Диапазон символов
[!abc] – Исключает диапазон символов
SELECT * FROM Customers
WHERE City LIKE 'ber%';

22. SELECT * FROM Customers
WHERE City LIKE '%es%';
SELECT * FROM Customers
WHERE City LIKE '_erlin';
SELECT * FROM Customers
WHERE City LIKE '[bsp]%';

23. The BETWEEN operator selects values within a
range. The values can be numbers, text, or dates.
SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20;
Or
SELECT * FROM Products
WHERE ProductName(NOT) BETWEEN 'C'
AND 'M';

24. SQL aliases are used to give a database table, or a
column in a table, a temporary name.
SELECT CustomerName AS Cust,
ContactName AS Somebody
FROM Customers;
SELECT CustomerName, Address+',
'+City+', '+PostalCode+', '+Country AS
Address
FROM Customers; - combine four columns

25. An SQL JOIN clause is used to combine
rows from two or more tables, based on
a common field between them.
The most common type of join is: SQL
INNER JOIN (simple join). An SQL INNER
JOIN return all rows from multiple
tables where exists connection between
them

27. SELECT Orders.OrderID,
Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers
ON Orders.CustomerID=Customers.CustomerID;

28.  INNER JOIN: Returns all rows when there is at
least one match in BOTH tables
If there are rows in the "Customers" table that
do not have matches in "Orders", these
customers will NOT be listed.

29. The LEFT JOIN keyword returns all rows from the
left table (table1), with the matching rows in the
right table (table2).
The LEFT JOIN keyword returns all the rows
from the left table (Customers), even if there
are no matches in the right table (Orders).

30. The FULL OUTER JOIN keyword returns
all rows from the left table (table1) and
from the right table (table2).

31. The SQL UNION operator combines the result of
two or more SELECT statements.
SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;

32. The SELECT INTO statement selects data from
one table and inserts it into a new table.
SELECT *
INTO CustomersBackup2013
FROM Customers;
WHERE Country='Germany';

33. The INSERT INTO SELECT statement selects data
from one table and inserts it into an existing
table. Any existing rows in the target table are
unaffected.
INSERT INTO Customers
(CustomerName, Country)
SELECT SupplierName, Country
FROM Suppliers;

34. We want to create a table called
"Persons" that contains five columns:
CREATE TABLE Persons
(PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255) );

35. SQL constraints are used to specify rules for
the data in a table.
 NOT NULL - Indicates that a column cannot
accept NULL values
CREATE TABLE PersonsNotNull
(P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255));

36.  UNIQUE - Ensures that each row for a
column must have a unique value:
CREATE TABLE Persons
(P_Id int NOT NULL UNIQUE,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255));

37.  PRIMARY KEY - Ensures that a column have an
unique identity which helps to find a record in
a table more easily and quickly.
CREATE TABLE Persons
(P_Id int NOT NULL PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
City varchar(255));

38.  FOREIGN KEY - Ensure the referential integrity
of the data in one table to match values in
another table
CREATE TABLE Orders
(O_Id int NOT NULL PRIMARY KEY,
OrderNo int NOT NULL,
P_Id int FOREIGN KEY REFERENCES
Persons(P_Id));

39.  CHECK - Ensures that the value in a column
meets a specific condition
CREATE TABLE Persons
(P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
CONSTRAINT chk_Person CHECK
(P_Id>0 AND City='Sandnes'));

40.  DEFAULT - is used to insert a default value into
a column.
CREATE TABLE Persons
(P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255) DEFAULT 'Sandnes');

41. Tables and databases can easily be
deleted/removed with the DROP statement.
DROP TABLE table_name;
DROP DATABASE database_name;
Only delete the data inside the table,
and not the table itself:
TRUNCATE TABLE table_name;

42. The ALTER TABLE statement is used to add,
delete, or modify columns in an existing table.
ALTER TABLE Persons
ALTER COLUMN DateOfBirth year(data
type);
ALTER TABLE Persons
DROP COLUMN DateOfBirth;

43. Very often we would like the value of the
primary key field to be created automatically
every time a new record is inserted.
CREATE TABLE Persons
(ID int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
PRIMARY KEY (ID));

44. In SQL, a view is a virtual table based on the
result-set of an SQL statement.
CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition;
DROP VIEW view_name;

45.  DATE - format YYYY-MM-DD
 DATETIME - format: YYYY-MM-DD HH:MM:SS
 SMALLDATETIME - format: YYYY-MM-DD
HH:MM:SS
 TIMESTAMP - format: a unique number

46. GETDATE() Returns the current date and time
DATEPART()
Returns a single part of a
date/time
DATEADD()
Adds or subtracts a specified time
interval from a date
DATEDIFF()
Returns the time between two
dates
CONVERT()
Displays date/time data in
different formats

47. NULL values represent missing unknown data
SELECT LastName,FirstName,Address
FROM Persons
WHERE Address IS(NOT) NULL;

48. Data type Access SQLServer Oracle MySQL PostgreSQL
boolean Yes/No Bit Byte N/A Boolean
integer
Number
(integer)
Int Number
Int
Integer
Int
Integer
float
Number
(single)
Float
Real
Number Float Numeric
currency Currency Money N/A N/A Money
string (fixed) N/A Char Char Char Char
string
(variable)
Text (<256)
Memo (65k+)
Varchar
Varchar
Varchar2
Varchar Varchar
binary object
OLE Object
Memo
Binary (fixed up to
8K)
Varbinary (<8K)
Image (<2GB)
Long
Raw
Blob
Text
Binary
Varbinary

49.  AVG() - Returns the average value
 COUNT() - Returns the number of rows
 FIRST() - Returns the first value
 LAST() - Returns the last value
 MAX() - Returns the largest value
 MIN() - Returns the smallest value
 SUM() - Returns the sum

50. Спасибо за внимание!