Sql basics

 an acronym for Structured Query
Language
 forms the backbone of most modern
database systems
 the language of databases
 a standard programming language for
querying and modifying data and
managing databases.
 a standard computer language for
accessing and manipulating databases.
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 SQL allows you to access a database
 SQL is an ANSI standard computer
language
 SQL can execute queries against a
database
 SQL can retrieve data from a database
 SQL can insert new records in a database
 SQL can delete records from a database
 SQL can update records

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 The first version of SQL, initially called SEQUEL, was
developed at IBM by Chamberlin and Boyce in the early
1970s.
 later formally standardized by the American National
Standards Institute (ANSI) in 1986.
 The first non-commercial non-SQL RDBMS, INGRES,
was developed in 1974 at the U.C. Berkely. Ingres
implemented a query language known as QUEL, which
was later supplanted in the marketplace by SQL.
 In the late 1970s, Relational Software, Inc. (now Oracle
Corp.) saw the potential of the concepts described by
Codd, Chamberlin, and Boyce and developed their own
SQL-based RDBMS.

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 Statements which may have a persistent effect on
schemas and data, or which may control transactions,
program flow, connections, sessions, or diagnostics.
 Queries which retrieve data based on specific criteria.
 Expressions which can produce either scalar values or
tables consisting of columns and rows of data.
 Predicates which specify conditions that can be
evaluated to SQL three-valued logic (3VL).

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 Clauses which are (in some cases optional) constituent
components of statements and queries.
 Whitespace is generally ignored in SQL statements and
queries, making it easier to format SQL code for
readability.
 SQL statements also include the semicolon (";")
statement terminator. Though not required on every
platform, it is defined as a standard part of the SQL
grammar.

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• 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.

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 Table: Enrol
 Class_Code
 Stu_Num
 Table:
 Enroll_Grade
Student_Info
 Table: Class
• Stu_Num  Class_Code
• Stu_LName  Crs_Cde
• Stu_Fname  Class_Section
 Class_Room
• Stu_MName  Pro_Num
• Stu_Bdate
• Stu_Hrs  Table: Course
• Stu_Class  Crs_Code
 Dept_Code
• Stu_GPA
 Crs_Description
• Stu_Transfer  Crs_Credit
• Dept_Code
• Stu_Phone 9

 With
SQL, we can query a database and
have a result set returned.

 SELECT LastName FROM Persons

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 SQL (Structured Query Language) is a
syntax for executing queries.
 SQL language also includes a syntax to
update, insert, and delete records.

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• SELECT - extracts data from a database table
• UPDATE - updates data in a database table
• DELETE - deletes data from a database table
• INSERT INTO - inserts new data into a
database table

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 Data Definition Language (DDL) part of SQL
permits database tables to be created or deleted.
 Define indexes (keys), specify links between
tables, and impose constraints between
database tables.

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• CREATE TABLE - creates a new database table
• ALTER TABLE - alters (changes) a database table
• DROP TABLE - deletes a database table
• CREATE INDEX - creates an index (search key)
• DROP INDEX - deletes an index

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 SELECT statement is used to select data
from a table.
 The tabular result is stored in a result table
(called the resultset).

 Syntax
SELECT column_name(s)
FROM table_name

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 Toselect the content of columns named
"LastName" and "FirstName", from the
database table called "Persons", use a

 SELECT statement like this:

 SELECT LastName,FirstName FROM
Persons

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 Toselect all columns from the "Persons"
table, use a * symbol instead of column
names, like this:

 SELECT * FROM Persons

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 The DISTINCT keyword is used to return
only distinct (different) values.
 The SELECT statement returns
information from table columns. But what
if we only want to select distinct
elements?
 With SQL, all we need to do is to add a
DISTINCT keyword to the SELECT
statement:
Syntax :
SELECT DISTINCT column_name(s)
FROM table_name
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 Toselect ALL values from the column
named "Company" we use a SELECT
statement like this:

 SELECT Company FROM Orders

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 Semicolon is the standard way to separate
each SQL statement in database systems
that allow more than one SQL
 statement to be executed in the same call
to the server.

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 DISTINCT keyword is used to return only
distinct (different) values.
 SELECT statement returns information
from table columns. But what if we only
want to select distinct elements?

 Syntax
SELECT DISTINCT column_name(s)
FROM table_name
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 Toselect ALL values from the column
named "Company" we use a SELECT
statement like this:

 SELECT Company FROM Orders

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 SELECT DISTINCT Company FROM
Orders

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 To
conditionally select data from a table, a
WHERE clause can be added to the
SELECT statement.

 Syntax

SELECT column FROM table
WHERE column operator value

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 Toselect only the persons living in the city
"Sandnes", we add a WHERE clause to
the SELECT statement:

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 Note that we have used single quotes
around the conditional values in the
examples.
 SQL uses single quotes around text values
(most database systems will also accept
double quotes). Numeric values
 should not be enclosed in quotes.

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 Thisis correct:
SELECT * FROM Persons WHERE
FirstName='Tove'

 This is wrong:

FirstName=Tove
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 This
is correct:
Year>1965

 Thisis wrong:
Year>'1965'

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 TheLIKE condition is used to specify a
search for a pattern in a column.

 Syntax
SELECT column FROM table
WHERE column LIKE pattern

A "%" sign can be used to define wildcards
(missing letters in the pattern) both before
and after the pattern.
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 The following SQL statement will return
persons with first names that start with
an 'O':
WHERE FirstName LIKE 'O%‘
WHERE FirstName LIKE '%a‘
WHERE FirstName LIKE '%la%'

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 INSERTINTO statement is used to insert
new rows into a table.

 Syntax
INSERT INTO table_name
VALUES (value1, value2,....)

INSERT INTO table_name (column1,
column2,...)
VALUES (value1, value2,....)
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 This "Persons" table:

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INSERT INTO Persons VALUES ('Hetland', 'Camilla',
'Hagabakka 24', 'Sandnes')

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Insert Data in Specified Columns
This "Persons" table:

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Tables:
 Customer
 Invoice
 Line
 Products
Identify the different fields per
table
 Inv_Number: inv,line  Line_Price: line
 Cus_Code: cus,inv
 Inv_Date: inv
 Prod_Code: prod,line
 Cus_Lname: cus  Prod_Descript: prod
 Cus_Fname: cus  Prod_Price: prod
 Cus_Initial: cus
 Prod_On_Hand: prod
 Cus_Areacode: cus
 Cus_Phone: cus  Vend_Code:prod
 Line_Units: line, prod

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Sql basics

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