ORACLE PL/SQL TUTORIALS - OVERVIEW - SQL COMMANDS

ORACLE PL/SQL TUTORIALS
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Structured Query Language
SQL is a standard computer language for accessing and manipulating databases.
What is SQL?
• SQL stands for Structured Query Language
• 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 in a database
• SQL is easy to learn
SQL is a Standard - BUT....
SQL is an ANSI (American National Standards Institute) standard
computer language for accessing and manipulating database systems.
SQL statements are used to retrieve and update data in a database. SQL
works with database programs like MS Access, DB2, Informix, MS SQL
Server, Oracle, Sybase, etc.
Unfortunately, there are many different versions of the SQL language,
but to be in compliance with the ANSI standard, they must support the
same major keywords in a similar manner (such as SELECT, UPDATE,
DELETE, INSERT, WHERE, and others).
Note: Most of the SQL database programs also have their own
proprietary extensions in addition to the SQL standard!
SQL 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":
LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

The table above contains three records (one for each person) and four
columns (LastName, FirstName, Address, and City).
SQL Queries
With SQL, we can query a database and have a result set returned.
A query like this:
SELECT LastName FROM Persons
Gives a result set like this:
LastName
Hansen
Svendson
Pettersen
Note: Some database systems require a semicolon at the end of the SQL
statement. We don't use the semicolon in our tutorials.
SQL Data Manipulation Language (DML)
SQL (Structured Query Language) is a syntax for executing queries. But
the SQL language also includes a syntax to update, insert, and delete
records.
These query and update commands together form the Data Manipulation
Language (DML) part of SQL:
 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
SQL Data Definition Language (DDL)
The Data Definition Language (DDL) part of SQL permits database tables
to be created or deleted. We can also define indexes (keys), specify links
between tables, and impose constraints between database tables.
The most important DDL statements in SQL are:
 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
The SELECT Statement
The SELECT statement is used to select data from a table. The tabular
result is stored in a result table (called the result-set).
Syntax
SELECT column_name(s)
FROM table_name
Select Some Columns
To select the columns named "LastName" and "FirstName", use a
SELECT statement like this:
SELECT LastName,FirstName FROM Persons
"Persons" table
Result
LastName FirstName
Hansen Ola
Svendson Tove
Pettersen Kari
Select All Columns
To select all columns from the "Persons" table, use a * symbol instead of
column names, like this:
SELECT * FROM Persons

Result
The Result Set
The result from a SQL query is stored in a result-set. Most database
software systems allow navigation of the result set with programming
functions, like: Move-To-First-Record, Get-Record-Content, Move-To-
Next-Record, etc.
Programming functions like these are not a part of this tutorial. To learn
about accessing data with function calls, please visit our ADO tutorial.
Semicolon after SQL Statements?
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.
Some SQL tutorials end each SQL statement with a semicolon. Is this
necessary? 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.
The SELECT DISTINCT Statement
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
Using the DISTINCT keyword
To select ALL values from the column named "Company" we use a
SELECT statement like this:
SELECT Company FROM Orders
"Orders" table
Company OrderNumber
Sega 3412
W3Schools 2312
Trio 4678
W3Schools 6798
Result
Company
Sega
W3Schools
Trio
W3Schools
Note that "W3Schools" is listed twice in the result-set.
To select only DIFFERENT values from the column named "Company" we
use a SELECT DISTINCT statement like this:
SELECT DISTINCT Company FROM Orders
Result:
Company
Sega
W3Schools
Trio
The WHERE clause is used to specify a selection criterion.

The WHERE Clause
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
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
Note: In some versions of SQL the <> operator may be written as !=
Using the WHERE Clause
To select only the persons living in the city "Sandnes", we add a WHERE
clause to the SELECT statement:
WHERE City='Sandnes'
"Persons" table
LastName FirstName Address City Year
Hansen Ola Timoteivn 10 Sandnes 1951
Svendson Tove Borgvn 23 Sandnes 1978
Svendson Stale Kaivn 18 Sandnes 1980
Pettersen Kari Storgt 20 Stavanger 1960

Result
LastName FirstName Address City Year
Hansen Ola Timoteivn 10 Sandnes 1951
Svendson Tove Borgvn 23 Sandnes 1978
Svendson Stale Kaivn 18 Sandnes 1980
Using Quotes
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.
For text values:
This is correct:
SELECT * FROM Persons WHERE FirstName='Tove'
This is wrong:
SELECT * FROM Persons WHERE FirstName=Tove
For numeric values:
This is correct:
SELECT * FROM Persons WHERE Year>1965
This is wrong:
SELECT * FROM Persons WHERE Year>'1965'
The LIKE Condition
The LIKE 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.
Using LIKE

The following SQL statement will return persons with first names that
start with an 'O':
WHERE FirstName LIKE 'O%'
end with an 'a':
WHERE FirstName LIKE '%a'
contain the pattern 'la':
WHERE FirstName LIKE '%la%'
The INSERT INTO Statement
The INSERT INTO statement is used to insert new rows into a table.
Syntax
INSERT INTO table_name
VALUES (value1, value2,....)
You can also specify the columns for which you want to insert data:
INSERT INTO table_name (column1, column2,...)
Insert a New Row
This "Persons" table:
And this SQL statement:
INSERT INTO Persons
VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes')

Will give this result:
Hetland Camilla Hagabakka 24 Sandnes
Insert Data in Specified Columns
This "Persons" table:
And This SQL statement:
INSERT INTO Persons (LastName, Address)
VALUES ('Rasmussen', 'Storgt 67')
Will give this result:
Rasmussen Storgt 67
The Update Statement
The UPDATE statement is used to modify the data in a table.
Syntax
UPDATE table_name
SET column_name = new_value
WHERE column_name = some_value
Person:
Nilsen Fred Kirkegt 56 Stavanger
Rasmussen Storgt 67

Update one Column in a Row
We want to add a first name to the person with a last name of
"Rasmussen":
UPDATE Person SET FirstName = 'Nina'
WHERE LastName = 'Rasmussen'
Result:
Rasmussen Nina Storgt 67
Update several Columns in a Row
We want to change the address and add the name of the city:
UPDATE Person
SET Address = 'Stien 12', City = 'Stavanger'
WHERE LastName = 'Rasmussen'
Result:
Rasmussen Nina Stien 12 Stavanger
The Delete Statement
The DELETE statement is used to delete rows in a table.
Syntax
DELETE FROM table_name
WHERE column_name = some_value
Person:

Rasmussen Nina Stien 12 Stavanger
Delete a Row
"Nina Rasmussen" is going to be deleted:
DELETE FROM Person WHERE LastName = 'Rasmussen'
Result
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:
or
DELETE * FROM table_name
SQL Syntax
Statement Syntax
AND / OR SELECT column_name(s)
FROM table_name
WHERE condition
AND|OR condition
ALTER TABLE (add
column)
ALTER TABLE table_name
ADD column_name datatype
ALTER TABLE (drop
column)
DROP COLUMN column_name
AS (alias for column) SELECT column_name AS column_alias
FROM table_name+
AS (alias for table) SELECT column_name
FROM table_name AS table_alias

BETWEEN SELECT column_name(s)
FROM table_name
WHERE column_name
BETWEEN value1 AND value2
CREATE DATABASE CREATE DATABASE database_name
CREATE INDEX CREATE INDEX index_name
ON table_name (column_name)
CREATE TABLE CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
.......
)
CREATE UNIQUE INDEX CREATE UNIQUE INDEX index_name
ON table_name (column_name)
CREATE VIEW CREATE VIEW view_name AS
FROM table_name
WHERE condition
DELETE FROM DELETE FROM table_name
(Note: Deletes the entire table!!) (Not the
structure)
or
WHERE condition
DROP DATABASE DROP DATABASE database_name
DROP INDEX DROP INDEX table_name.index_name
DROP TABLE DROP TABLE table_name
GROUP BY SELECT column_name1,SUM(column_name2)
FROM table_name
GROUP BY column_name1
HAVING SELECT column_name1,SUM(column_name2)
FROM table_name
GROUP BY column_name1
HAVING SUM(column_name2) condition value
IN SELECT column_name(s)
FROM table_name
WHERE column_name
IN (value1,value2,..)
INSERT INTO INSERT INTO table_name

or
INSERT INTO table_name
(column_name1, column_name2,...)
LIKE SELECT column_name(s)
FROM table_name
WHERE column_name
LIKE pattern
ORDER BY SELECT column_name(s)
FROM table_name
ORDER BY column_name [ASC|DESC]
SELECT SELECT column_name(s)
FROM table_name
SELECT * SELECT *
FROM table_name
SELECT DISTINCT SELECT DISTINCT column_name(s)
FROM table_name
SELECT INTO
(used to create backup
copies of tables)
SELECT *
INTO new_table_name
FROM original_table_name
or
INTO new_table_name
FROM original_table_name
TRUNCATE TABLE
(deletes only the data
inside the table)
TRUNCATE TABLE table_name
UPDATE UPDATE table_name
SET column_name=new_value
[, column_name=new_value]
WHERE column_name=some_value
WHERE SELECT column_name(s)
FROM table_name
WHERE condition
BETWEEN ... AND
The BETWEEN ... AND operator selects a range of data between two
values. These values can be numbers, text, or dates.
SELECT column_name FROM table_name
WHERE column_name

BETWEEN value1 AND value2
Original Table (used in the examples)
Nordmann Anna Neset 18 Sandnes
Example 1
To display the persons alphabetically between (and including) "Hansen"
and exclusive "Pettersen", use the following SQL:
SELECT * FROM Persons WHERE LastName
BETWEEN 'Hansen' AND 'Pettersen'
Result:
IMPORTANT! The BETWEEN...AND operator is treated differently in
different databases. With some databases a person with the LastName
of "Hansen" or "Pettersen" will not be listed (BETWEEN..AND only
selects fields that are between and excluding the test values). With
some databases a person with the last name of "Hansen" or "Pettersen"
will be listed (BETWEEN..AND selects fields that are between and
including the test values). With other databases a person with the last
name of "Hansen" will be listed, but "Pettersen" will not be listed
(BETWEEN..AND selects fields between the test values, including the
first test value and excluding the last test value). Therefore: Check how
your database treats the BETWEEN....AND operator!
Example 2
To display the persons outside the range used in the previous example,
use the NOT operator:
SELECT * FROM Persons WHERE LastName
NOT BETWEEN 'Hansen' AND 'Pettersen'

Result:
The ORDER BY keyword is used to sort the result.
Sort the Rows
The ORDER BY clause is used to sort the rows.
Orders:
Company OrderNumber
Sega 3412
ABC Shop 5678
W3Schools 2312
W3Schools 6798
Example
To display the companies in alphabetical order:
SELECT Company, OrderNumber FROM Orders
ORDER BY Company
Result:
Company OrderNumber
ABC Shop 5678
Sega 3412
W3Schools 6798
W3Schools 2312
Example
To display the companies in alphabetical order AND the ordernumbers in
numerical order:

ORDER BY Company, OrderNumber
Result:
Company OrderNumber
ABC Shop 5678
Sega 3412
W3Schools 2312
W3Schools 6798
Example
To display the companies in reverse alphabetical order:
ORDER BY Company DESC
Result:
Company OrderNumber
W3Schools 6798
W3Schools 2312
Sega 3412
ABC Shop 5678
Example
To display the companies in reverse alphabetical order AND the
ordernumbers in numerical order:
ORDER BY Company DESC, OrderNumber ASC
Result:
Company OrderNumber
W3Schools 2312
W3Schools 6798
Sega 3412
ABC Shop 5678
IN

The IN operator may be used if you know the exact value you want to
return for at least one of the columns.
SELECT column_name FROM table_name
WHERE column_name IN (value1,value2,..)
Example 1
To display the persons with LastName equal to "Hansen" or "Pettersen",
use the following SQL:
WHERE LastName IN ('Hansen','Pettersen')
Result:
AND & OR
AND and OR join two or more conditions in a WHERE clause.
The AND operator displays a row if ALL conditions listed are true. The
OR operator displays a row if ANY of the conditions listed are true.
Svendson Stephen Kaivn 18 Sandnes

Example
Use AND to display each person with the first name equal to "Tove", and
the last name equal to "Svendson":
WHERE FirstName='Tove'
AND LastName='Svendson'
Result:
Example
Use OR to display each person with the first name equal to "Tove", or
the last name equal to "Svendson":
WHERE firstname='Tove'
OR lastname='Svendson'
Result:
Example
You can also combine AND and OR (use parentheses to form complex
expressions):
SELECT * FROM Persons WHERE
(FirstName='Tove' OR FirstName='Stephen')
AND LastName='Svendson'
Result:

Aggregate functions (like SUM) often need an added GROUP BY functionality.
GROUP BY...
GROUP BY... was added to SQL because aggregate functions (like SUM)
return the aggregate of all column values every time they are called, and
without the GROUP BY function it was impossible to find the sum for
each individual group of column values.
The syntax for the GROUP BY function is:
SELECT column,SUM(column) FROM table GROUP BY column
GROUP BY Example
This "Sales" Table:
Company Amount
W3Schools 5500
IBM 4500
W3Schools 7100
And This SQL:
SELECT Company, SUM(Amount) FROM Sales
Returns this result:
Company SUM(Amount)
W3Schools 17100
IBM 17100
W3Schools 17100
The above code is invalid because the column returned is not part of an
aggregate. A GROUP BY clause will solve this problem:
SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company

Returns this result:
Company SUM(Amount)
W3Schools 12600
IBM 4500
HAVING...
HAVING... was added to SQL because the WHERE keyword could not be
used against aggregate functions (like SUM), and without HAVING... it
would be impossible to test for result conditions.
The syntax for the HAVING function is:
SELECT column,SUM(column) FROM table
GROUP BY column
HAVING SUM(column) condition value
This "Sales" Table:
Company Amount
W3Schools 5500
IBM 4500
W3Schools 7100
This SQL:
SELECT Company,SUM(Amount) FROM Sales
GROUP BY Company
HAVING SUM(Amount)>10000
Returns this result
Company SUM(Amount)
W3Schools 12600
The SELECT INTO Statement

The SELECT INTO statement is most often used to create backup copies
of tables or for archiving records.
Syntax
SELECT column_name(s) INTO newtable [IN externaldatabase]
FROM source
Make a Backup Copy
The following example makes a backup copy of the "Persons" table:
SELECT * INTO Persons_backup
FROM Persons
The IN clause can be used to copy tables into another database:
SELECT Persons.* INTO Persons IN 'Backup.mdb'
FROM Persons
If you only want to copy a few fields, you can do so by listing them after
the SELECT statement:
SELECT LastName,FirstName INTO Persons_backup
FROM Persons
You can also add a WHERE clause. The following example creates a
"Persons_backup" table with two columns (FirstName and LastName)
by extracting the persons who lives in "Sandnes" from the "Persons"
table:
SELECT LastName,Firstname INTO Persons_backup
FROM Persons
WHERE City='Sandnes'
Selecting data from more than one table is also possible. The following
example creates a new table "Empl_Ord_backup" that contains data
from the two tables Employees and Orders:
SELECT Employees.Name,Orders.Product
INTO Empl_Ord_backup
FROM Employees
INNER JOIN Orders
ON Employees.Employee_ID=Orders.Employee_ID

ALTER TABLE
The ALTER TABLE statement is used to add or drop columns in an
existing table.
ADD column_name datatype
DROP COLUMN column_name
Note: Some database systems don't allow the dropping of a column in a
database table (DROP COLUMN column_name).
Person:
LastName FirstName Address
Pettersen Kari Storgt 20
Example
To add a column named "City" in the "Person" table:
ALTER TABLE Person ADD City varchar(30)
Result:
Pettersen Kari Storgt 20
Example
To drop the "Address" column in the "Person" table:
ALTER TABLE Person DROP COLUMN Address
Result:
LastName FirstName City
Pettersen Kari
SQL has a lot of built-in functions for counting and calculations.

Function Syntax
The syntax for built-in SQL functions is:
SELECT function(column) FROM table
Types of Functions
There are several basic types and categories of functions in SQL. The
basic types of functions are:
• Aggregate Functions
• Scalar functions
Aggregate functions
Aggregate functions operate against a collection of values, but return a
single value.
Note: If used among many other expressions in the item list of a SELECT
statement, the SELECT must have a GROUP BY clause!!
"Persons" table (used in most examples)
Name Age
Hansen, Ola 34
Svendson, Tove 45
Pettersen, Kari 19
Aggregate functions in MS Access
Function Description
AVG(column) Returns the average value of a column
COUNT(column) Returns the number of rows (without a NULL
value) of a column
COUNT(*) Returns the number of selected rows
FIRST(column) Returns the value of the first record in the
specified field
LAST(column) Returns the value of the last record in the
specified field

MAX(column) Returns the highest value of a column
MIN(column) Returns the lowest value of a column
STDEV(column)
STDEVP(column)
SUM(column) Returns the total sum of a column
VAR(column)
VARP(column)
Aggregate functions in SQL Server
AVG(column) Returns the average value of a column
BINARY_CHECKSUM
CHECKSUM
CHECKSUM_AGG
COUNT(column) Returns the number of rows (without a NULL
value) of a column
COUNT(*) Returns the number of selected rows
COUNT(DISTINCT
column)
Returns the number of distinct results
FIRST(column) Returns the value of the first record in the
specified field (not supported in SQLServer2K)
LAST(column) Returns the value of the last record in the
specified field (not supported in SQLServer2K)
MAX(column) Returns the highest value of a column
MIN(column) Returns the lowest value of a column
STDEV(column)
STDEVP(column)
SUM(column) Returns the total sum of a column
VAR(column)
VARP(column)
Scalar functions
Scalar functions operate against a single value, and return a single value
based on the input value.
Useful Scalar Functions in MS Access

UCASE(c) Converts a field to upper case
LCASE(c) Converts a field to lower case
MID(c,start[,end]) Extract characters from a text field
LEN(c) Returns the length of a text field
INSTR(c) Returns the numeric position of a named
character within a text field
LEFT(c,number_of_char) Return the left part of a text field requested
RIGHT(c,number_of_char) Return the right part of a text field requested
ROUND(c,decimals) Rounds a numeric field to the number of
decimals specified
MOD(x,y) Returns the remainder of a division operation
NOW() Returns the current system date
FORMAT(c,format) Changes the way a field is displayed
DATEDIFF(d,date1,date2) Used to perform date calculations
UNION
The UNION command is used to select related information from two
tables, much like the JOIN command. However, when using the UNION
command all selected columns need to be of the same data type.
Note: With UNION, only distinct values are selected.
SQL Statement 1
UNION
SQL Statement 2
Employees_Norway:
Employee_ID E_Name
01 Hansen, Ola
02 Svendson, Tove
03 Svendson, Stephen
04 Pettersen, Kari
Employees_USA:
Employee_ID E_Name

01 Turner, Sally
02 Kent, Clark
03 Svendson, Stephen
04 Scott, Stephen
Using the UNION Command
Example
List all different employee names in Norway and USA:
SELECT E_Name FROM Employees_Norway
UNION
SELECT E_Name FROM Employees_USA
Result
Name
Hansen, Ola
Svendson, Tove
Svendson, Stephen
Pettersen, Kari
Turner, Sally
Kent, Clark
Scott, Stephen
Note: This command cannot be used to list all employees in Norway and
USA. In the example above we have two employees with equal names,
and only one of them is listed. The UNION command only selects distinct
values.
UNION ALL
The UNION ALL command is equal to the UNION command, except that
UNION ALL selects all values.
SQL Statement 1
UNION ALL
SQL Statement 2
Using the UNION ALL Command

Example
List all employees in Norway and USA:
SELECT E_Name FROM Employees_Norway
UNION ALL
SELECT E_Name FROM Employees_USA
Result
Name
Hansen, Ola
Svendson, Tove
Svendson, Stephen
Pettersen, Kari
Turner, Sally
Kent, Clark
Svendson, Stephen
Scott, Stephen

NewyorkSys is one of the leading top Training and Consulting
Company in US. Newyorksys have certified trainers. We will provide
Online Training, Fast Track online training, with job assistance. We
are providing excellent Training in all courses. Faculty from top
MNC’s with highly skilled domain expertise will train & guide you with
real time examples, project explanation. We also help you in resume
preparation and provide job assistance till you get job.
Oracle
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• 10g / 11g DBA
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ORACLE PL/SQL TUTORIALS - OVERVIEW - SQL COMMANDS

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