Sql slid

 SQL
 SQL is a standard language for accessing and manipulating databases.
 What is SQL?
 SQL stands for Structured Query Language
 SQL lets you access and manipulate databases
 SQL is an ANSI (American National Standards Institute) standard
 What Can SQL do?
 SQL can execute queries against a database
 SQL can retrieve data from a database
 SQL can insert records in a database
 SQL can update records in a database
 SQL can delete records from a database
 SQL can create new databases
 SQL can create new tables in a database

 SQL can create stored procedures in a database
 SQL can create views in a database
 SQL can set permissions on tables, procedures, and views
 SQL is a Standard - BUT....
 Although SQL is an ANSI (American National Standards
Institute) standard, there are many different versions of the
SQL language.
 However, to be compliant with the ANSI standard, they all
support at least the major commands (such as SELECT,
UPDATE, DELETE, INSERT, WHERE) in a similar manner.
 Note: Most of the SQL database programs also have their
own proprietary extensions in addition to the SQL
standard!

 RDBMS
 RDBMS stands for Relational Database Management System.
 RDBMS is the basis for SQL, and for all modern database
systems like MS SQL Server, IBM DB2, Oracle, MySQL, and
Microsoft Access.
 The data in RDBMS is stored in database objects called tables.
 A table is a collection of related data entries and it consists of
columns and rows.
 Database Tables
 A database most often contains one or more tables. Each table is
identified by a name (e.g. "Customers" or "Orders"). Tables
contain records (rows) with data.

 Below is an example of a table called "Persons":

P_Id LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger

 The table above contains three records (one for each
person) and five columns (P_Id, LastName, FirstName,
Address, and City).
 Keep in Mind That...
 SQL is not case sensitive

 Semicolon after SQL Statements?
 Some database systems require a semicolon at the end of each
SQL statement.
 We are using MS Access and SQL Server 2000 and we do not
have to put a semicolon after each SQL statement, but some
database programs force you to use it.
 SQL DML and DDL
 SQL can be divided into two parts: The Data Manipulation
Language (DML) and the Data Definition Language (DDL).
 The query and update commands form the DML part of SQL:
 SELECT - extracts data from a database
 UPDATE - updates data in a database
 DELETE - deletes data from a database
 INSERT INTO - inserts new data into a database

 The DDL part of SQL permits database tables to be created or deleted.
It also defines indexes (keys), specifies links between tables, and
imposes constraints between tables. The most important DDL
statements in SQL are:
 CREATE DATABASE - creates a new database
 ALTER DATABASE - modifies a database
 CREATE TABLE - creates a new table
 ALTER TABLE - modifies a table
 DROP TABLE - deletes a table
 CREATE INDEX - creates an index (search key)
 DROP INDEX - deletes an index
 The SQL SELECT Statement
 The SELECT statement is used to select data from a database.
 The result is stored in a result table, called the result-set.

 SQL SELECT Syntax
 SELECT column_name(s)
FROM table_name
 and
 SELECT * FROM table_name
 The WHERE Clause
 The WHERE clause is used to extract only those records
that fulfill a specified criterion.
 SQL WHERE Syntax
FROM table_name
WHERE column_name operator value

 Operators Allowed in the WHERE Clause
 With the WHERE clause, the following operators can be used:

Operator Description
= Equal
<> Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
IN If you know the exact value you want to return for at least
one of the columns

 The AND & OR Operators
 The AND operator displays a record if both the first condition
and the second condition is true.
 The OR operator displays a record if either the first condition or
the second condition is true.
 We use the following SELECT statement:
 SELECT * FROM Persons
WHERE FirstName='Chandra'
AND LastName='Ajad'
 Combining AND & OR
 You can also combine AND and OR (use parenthesis to form
complex expressions).
 Now we want to select only the persons with the last name equal
to "Svendson" AND the first name equal to "Tove" OR to "Ola":

 We use the following SELECT statement:
 SELECT * FROM Persons WHERE
LastName='Svendson'
AND (FirstName='Tove' OR FirstName='Ola')
 The result-set will look like this:

P_Id LastName FirstName Address City
2 Svendson Tove Borgvn 23 Sandnes

 The ORDER BY Keyword
 The ORDER BY keyword is used to sort the result-set by a specified
column.
 The ORDER BY keyword sort the records in ascending order by default.
 If you want to sort the records in a descending order, you can use the
DESC keyword.

 SQL ORDER BY Syntax
FROM table_name
ORDER BY column_name(s) ASC|DESC
 The INSERT INTO Statement
 The INSERT INTO statement is used to insert a new row in a
table.
 SQL INSERT INTO Syntax
 It is possible to write the INSERT INTO statement in two forms.
 The first form doesn't specify the column names where the data
will be inserted, only their values:
 INSERT INTO table_name
VALUES (value1, value2, value3,...)

 Insert Data Only in Specified Columns
 It is also possible to only add data in specific columns.
 The following SQL statement will add a new row, but only add
data in the "P_Id", "LastName" and the "FirstName" columns:
 INSERT INTO Persons (P_Id, LastName, FirstName)
VALUES (5, 'Tjessem', 'Jakob')
 The UPDATE Statement
 The UPDATE statement is used to update existing records in a
table.
 SQL UPDATE Syntax
 UPDATE table_name
SET column1=value, column2=value2,...
WHERE some_column=some_value

 The DELETE Statement
 The DELETE statement is used to delete rows in a table.
 SQL DELETE Syntax
 DELETE FROM table_name
WHERE some_column=some_value
 Delete All Rows
 It is possible to delete all rows in a table without deleting the table. This
means that the table structure, attributes, and indexes will be intact:
 DELETE FROM table_name
or
DELETE * FROM table_name
 SQL JOIN
 The JOIN keyword is used in an SQL statement to query data from two
or more tables, based on a relationship between certain columns in
these tables.

 Tables in a database are often related to each other with keys.
 A primary key is a column (or a combination of columns) with a unique
value for each row. Each primary key value must be unique within the
table. The purpose is to bind data together, across tables, without
repeating all of the data in every table.
 Different SQL JOINs
 Before we continue with examples, we will list the types of JOIN you
can use, and the differences between them.
 JOIN: Return rows when there is at least one match in both tables
 LEFT JOIN: Return all rows from the left table, even if there are no
matches in the right table
 RIGHT JOIN: Return all rows from the right table, even if there are no
matches in the left table
 FULL JOIN: Return rows when there is a match in one of the tables

 SQL INNER JOIN Keyword
 The INNER JOIN keyword return rows when there is at least one match in both
tables.
 SQL INNER JOIN Syntax
FROM table_name1
INNER JOIN table_name2
ON table_name1.column_name=table_name2.column_name

 SQL LEFT JOIN Keyword
 The LEFT JOIN keyword returns all rows from the left table (table_name1),
even if there are no matches in the right table (table_name2).
 SQL LEFT JOIN Syntax
FROM table_name1
LEFT JOIN table_name2

 SQL RIGHT JOIN Keyword
 The RIGHT JOIN keyword returns all the rows from the right table
(table_name2), even if there are no matches in the left table (table_name1).
 SQL RIGHT JOIN Syntax
FROM table_name1
RIGHT JOIN table_name2

 SQL FULL JOIN Keyword
 The FULL JOIN keyword return rows when there is a match in one of the
tables.
 SQL FULL JOIN Syntax
FROM table_name1
FULL JOIN table_name2

 The SQL UNION Operator
 The UNION operator is used to combine the result-set of two or more
SELECT statements.
 Notice that each SELECT statement within the UNION must have the
same number of columns. The columns must also have similar data
types. Also, the columns in each SELECT statement must be in the
same order.
 SQL UNION Syntax
 SELECT column_name(s) FROM table_name1
UNION
SELECT column_name(s) FROM table_name2
 The SQL SELECT INTO Statement
 The SELECT INTO statement selects data from one table and inserts it
into a different table.
 The SELECT INTO statement is most often used to create backup
copies of tables.

 SQL SELECT INTO Syntax
 We can select all columns into the new table:
 SELECT *
INTO new_table_name [IN externaldatabase]
FROM old_tablename
 We use the following SQL statement:
 SELECT *
INTO Persons_Backup
FROM Persons
 SQL SELECT INTO - Joined Tables
 Selecting data from more than one table is also possible.
 The following example creates a "Persons_Order_Backup" table
contains data from the two tables "Persons" and "Orders":

 SELECT Persons.LastName,Orders.OrderNo
INTO Persons_Order_Backup
FROM Persons
INNER JOIN Orders
ON Persons.P_Id=Orders.P_Id
 SQL CREATE DATABASE Syntax
 CREATE DATABASE database_name
 The CREATE TABLE Statement
 The CREATE TABLE statement is used to create a table in a database.
 SQL CREATE TABLE Syntax
 CREATE TABLE table_name
(
column_name1 data_type,
....
)

 SQL NOT NULL Constraint
 The NOT NULL constraint enforces a column to NOT accept NULL
values.
 The NOT NULL constraint enforces a field to always contain a value.
This means that you cannot insert a new record, or update a record
without adding a value to this field.
 The following SQL enforces the "P_Id" column and the "LastName"
column to not accept NULL values:
 CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

 SQL UNIQUE Constraint
 The UNIQUE constraint uniquely identifies each record in a
database table.
 The UNIQUE and PRIMARY KEY constraints both provide a
guarantee for uniqueness for a column or set of columns.
 A PRIMARY KEY constraint automatically has a UNIQUE
constraint defined on it.
 Note that you can have many UNIQUE constraints per table, but
only one PRIMARY KEY constraint per table.
 SQL PRIMARY KEY Constraint
 The PRIMARY KEY constraint uniquely identifies each record in
a database table.
 Primary keys must contain unique values.
 A primary key column cannot contain NULL values.

 Each table should have a primary key, and each table can have
only ONE primary key.
 CREATE TABLE Persons
(
P_Id int NOT NULL PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
 SQL FOREIGN KEY Constraint
 A FOREIGN KEY in one table points to a PRIMARY KEY in
another table.
 Let's illustrate the foreign key with an example. Look at the
following two tables:

 CREATE TABLE Orders
(
O_Id int NOT NULL PRIMARY KEY,
OrderNo int NOT NULL,
P_Id int FOREIGN KEY REFERENCES Persons(P_Id)
)
 To DROP a FOREIGN KEY Constraint
 To drop a FOREIGN KEY constraint, use the following SQL:
 ALTER TABLE Orders
DROP CONSTRAINT fk_PerOrders
 Indexes
 An index can be created in a table to find data more quickly and efficiently.
 The users cannot see the indexes, they are just used to speed up
searches/queries.
 Note: Updating a table with indexes takes more time than updating a table
without (because the indexes also need an update). So you should only create
indexes on columns (and tables) that will be frequently searched against.

 SQL CREATE INDEX Syntax
 Creates an index on a table. Duplicate values are allowed:
 CREATE INDEX index_name
ON table_name (column_name)
 The DROP INDEX Statement
 The DROP INDEX statement is used to delete an index in a table.
 DROP INDEX Syntax for MS Access:
 DROP INDEX index_name ON table_name
 DROP INDEX Syntax for MS SQL Server:
 DROP INDEX table_name.index_name
 The ALTER TABLE Statement
 The ALTER TABLE statement is used to add, delete, or modify columns
in an existing table.
 SQL ALTER TABLE Syntax

 To add a column in a table, use the following syntax:
 ALTER TABLE table_name
ADD column_name datatype
 To delete a column in a table, use the following syntax (notice
that some database systems don't allow deleting a column):
DROP COLUMN column_name
 To change the data type of a column in a table, use the following
syntax:
ALTER COLUMN column_name datatype
 The DROP INDEX Statement
 The DROP INDEX statement is used to delete an index in a
table.

 DROP INDEX Syntax for MS Access:
 DROP INDEX index_name ON table_name
 DROP INDEX Syntax for MS SQL Server:
 DROP INDEX table_name.index_name
 SQL CREATE VIEW Statement
 In SQL, a view is a virtual table based on the result-set of an SQL statement.
 A view contains rows and columns, just like a real table. The fields in a view are
fields from one or more real tables in the database.
 You can add SQL functions, WHERE, and JOIN statements to a view and
present the data as if the data were coming from one single table.

 SQL CREATE VIEW Syntax
 CREATE VIEW view_name AS
SELECT column_name(s)
FROM table_name
WHERE condition

 Microsoft Access Data Types

Data type Description Storage

Text Use for text or combinations of text and numbers. 255
characters maximum

Memo Memo is used for larger amounts of text. Stores up to
65,536 characters. Note: You cannot sort a memo field.
However, they are searchable

Byte Allows whole numbers from 0 to 255 1 byte

Integer Allows whole numbers between -32,768 and 32,767 2 bytes

Long Allows whole numbers between -2,147,483,648 and 4 bytes
2,147,483,647
Single Single precision floating-point. Will handle most 4 bytes
decimals

Double Double precision floating-point. Will handle most decimals 8 bytes
Currency Use for currency. Holds up to 15 digits of whole dollars, plus 4 8 bytes
decimal places. Tip: You can choose which country's currency to
use
AutoNumber AutoNumber fields automatically give each record its own 4 bytes
number, usually starting at 1
Date/Time Use for dates and times 8 bytes
Yes/No A logical field can be displayed as Yes/No, True/False, or On/Off. 1 bit
In code, use the constants True and False (equivalent to -1 and
0).Note: Null values are not allowed in Yes/No fields
Ole Object Can store pictures, audio, video, or other BLOBs (Binary Large up to 1GB
OBjects)
Hyperlink Contain links to other files, including web pages
Lookup Let you type a list of options, which can then be chosen from a 4 bytes
Wizard drop-down list

 MySQL Data Types
 In MySQL there are three main types : text, number, and Date/Time
types.
 Text types:

Data type Description
CHAR(size) Holds a fixed length string (can contain letters, numbers, and special
characters). The fixed size is specified in parenthesis. Can store up to
255 characters
VARCHAR(size) Holds a variable length string (can contain letters, numbers, and
special characters). The maximum size is specified in parenthesis.
Can store up to 255 characters. Note: If you put a greater value than
255 it will be converted to a TEXT type
TINYTEXT Holds a string with a maximum length of 255 characters

TEXT Holds a string with a maximum length of 65,535 characters
BLOB For BLOBs (Binary Large OBjects). Holds up to 65,535 bytes of data
MEDIUMTEXT Holds a string with a maximum length of 16,777,215 characters
MEDIUMBLOB For BLOBs (Binary Large OBjects). Holds up to 16,777,215 bytes of data
LONGTEXT Holds a string with a maximum length of 4,294,967,295 characters
LONGBLOB For BLOBs (Binary Large OBjects). Holds up to 4,294,967,295 bytes of data
ENUM(x,y,z,etc.) Let you enter a list of possible values. You can list up to 65535 values in an
ENUM list. If a value is inserted that is not in the list, a blank value will be
inserted.
Note: The values are sorted in the order you enter them.

You enter the possible values in this format: ENUM('X','Y','Z')
SET Similar to ENUM except that SET may contain up to 64 list items and can
store more than one choice

 Number types:

TINYINT(size) -128 to 127 normal. 0 to 255 UNSIGNED*. The maximum number of
digits may be specified in parenthesis
SMALLINT(size) -32768 to 32767 normal. 0 to 65535 UNSIGNED*. The maximum
number of digits may be specified in parenthesis
MEDIUMINT(size) -8388608 to 8388607 normal. 0 to 16777215 UNSIGNED*. The
maximum number of digits may be specified in parenthesis
INT(size) -2147483648 to 2147483647 normal. 0 to 4294967295 UNSIGNED*. The
maximum number of digits may be specified in parenthesis
BIGINT(size) -9223372036854775808 to 9223372036854775807 normal. 0 to
18446744073709551615 UNSIGNED*. The maximum number of digits
may be specified in parenthesis

FLOAT(size,d) A small number with a floating decimal point. The maximum number
of digits may be specified in the size parameter. The maximum number
of digits to the right of the decimal point is specified in the d
parameter
DOUBLE(size,d) A large number with a floating decimal point. The maximum number of digits
may be specified in the size parameter. The maximum number of digits to the
right of the decimal point is specified in the d parameter
DECIMAL(size,d) A DOUBLE stored as a string , allowing for a fixed decimal point. The
maximum number of digits may be specified in the size parameter. The
maximum number of digits to the right of the decimal point is specified in the
d parameter
 *The integer types have an extra option called UNSIGNED. Normally,
the integer goes from an negative to positive value. Adding the
UNSIGNED attribute will move that range up so it starts at zero instead
of a negative number.

 Date types:

DATE() A date. Format: YYYY-MM-DD
Note: The supported range is from '1000-01-01' to '9999-12-31'
DATETIME() *A date and time combination. Format: YYYY-MM-DD HH:MM:SS
Note: The supported range is from '1000-01-01 00:00:00' to '9999-12-31
23:59:59'
TIMESTAMP() *A timestamp. TIMESTAMP values are stored as the number of seconds
since the Unix epoch ('1970-01-01 00:00:00' UTC). Format: YYYY-MM-
DD HH:MM:SS
Note: The supported range is from '1970-01-01 00:00:01' UTC to '2038-
01-09 03:14:07' UTC
TIME() A time. Format: HH:MM:SS
Note: The supported range is from '-838:59:59' to '838:59:59'

YEAR() A year in two-digit or four-digit format.
Note: Values allowed in four-digit format: 1901 to 2155. Values
allowed in two-digit format: 70 to 69, representing years from 1970
to 2069

 *Even if DATETIME and TIMESTAMP return the same format, they
work very differently. In an INSERT or UPDATE query, the
TIMESTAMP automatically set itself to the current date and time.
TIMESTAMP also accepts various formats, like YYYYMMDDHHMMSS,
YYMMDDHHMMSS, YYYYMMDD, or YYMMDD.
 SQL Server Data Types
 Character strings:

char(n) Fixed-length character string. Maximum 8,000 characters n
varchar(n) Variable-length character string. Maximum 8,000 characters
varchar(max) Variable-length character string. Maximum 1,073,741,824 characters
text Variable-length character string. Maximum 2GB of text data

 Unicode strings:

nchar(n) Fixed-length Unicode data. Maximum 4,000 characters
nvarchar(n) Variable-length Unicode data. Maximum 4,000 characters
nvarchar(max) Variable-length Unicode data. Maximum 536,870,912
characters
ntext Variable-length Unicode data. Maximum 2GB of text data

 Binary types:

bit Allows 0, 1, or NULL
binary(n) Fixed-length binary data. Maximum 8,000 bytes
varbinary(n) Variable-length binary data. Maximum 8,000 bytes
varbinary(max) Variable-length binary data. Maximum 2GB
image Variable-length binary data. Maximum 2GB

 Number types:
tinyint Allows whole numbers from 0 to 255 1 byte
smallint Allows whole numbers between -32,768 and 32,767 2 bytes
int Allows whole numbers between -2,147,483,648 and 2,147,483,647 4 bytes

bigint Allows whole numbers between - 8 bytes
9,223,372,036,854,775,808 and
9,223,372,036,854,775,807
decimal(p,s) Fixed precision and scale numbers. 5-17 bytes
Allows numbers from -10^38 +1 to 10^38 –1.
The p parameter indicates the maximum total number
of digits that can be stored (both to the left and to the
right of the decimal point). p must be a value from 1 to
38. Default is 18.
The s parameter indicates the maximum number of
digits stored to the right of the decimal point. s must
be a value from 0 to p. Default value is 0

numeric(p,s) Fixed precision and scale numbers. 5-17 bytes
Allows numbers from -10^38 +1 to 10^38 –1.

The p parameter indicates the maximum
total number of digits that can be stored
(both to the left and to the right of the
decimal point). p must be a value from 1 to
38. Default is 18.

The s parameter indicates the maximum
number of digits stored to the right of the
decimal point. s must be a value from 0 to
p. Default value is 0
smallmoney Monetary data from -214,748.3648 to 4 bytes
214,748.3647
money Monetary data from - 8 bytes
922,337,203,685,477.5808 to
922,337,203,685,477.5807

float(n) Floating precision number data from -1.79E + 308 to 1.79E + 308. 4 or 8 bytes
The n parameter indicates whether the field should hold 4 or 8 bytes.
float(24) holds a 4-byte field and float(53) holds an 8-byte field.
Default value of n is 53.
real Floating precision number data from -3.40E + 38 to 3.40E + 38 4 bytes

 Date types:

datetime From January 1, 1753 to December 31, 9999 with an accuracy of 3.33 8 bytes
milliseconds
datetime2 From January 1, 0001 to December 31, 9999 with an accuracy of 100 6-8 bytes
nanoseconds
smalldateti From January 1, 1900 to June 6, 2079 with an accuracy of 1 minute 4 bytes
me

date Store a date only. From January 1, 0001 to December 31, 3 bytes
9999

time Store a time only to an accuracy of 100 nanoseconds 3-5 bytes

datetimeoffset The same as datetime2 with the addition of a time 8-10 bytes
zone offset
timestamp Stores a unique number that gets updated every time a
row gets created or modified. The timestamp value is
based upon an internal clock and does not correspond
to real time. Each table may have only one timestamp
variable

 Other data types:


sql_variant Stores up to 8,000 bytes of data of various data types, except text, ntext,
and timestamp

uniqueidentifier Stores a globally unique identifier (GUID)

xml Stores XML formatted data. Maximum 2GB

cursor Stores a reference to a cursor used for database operations

table Stores a result-set for later processing

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