Oracle basic queries

 CHAR(size)
- used to store fixed length string.
-max size 255 character.
 VARCHAR2(size)
-used to store variable length string .
-it can store letter, number and
punctuation marks.
-max size 4000 character.
• VARCHAR(size)
-same as CHAR(size),but speed is
less.
-it is also used for storing string of
variable length.
• NUMBER(precision , scale)
-’precision’ total no of digits that can
be stored.
-’scale’ total no of digits after decimal.
e.g. : NUMBER(4) or NUMBER(4,2)
or NUMBER.
Actual
Data
Defined
As
Stored As
123456.78
9
NUMBER(
6,2)
1234.79
123456.78
9
NUMBER(
6)
123457
123456.78
9
NUMBER(
6,-2)
123500
123456.78
9
NUMBER 123456.78
9

 DATE
 LONG
-used to store variable length
text, of very large size
-max size 2GB.
Binary Types
• RAW(size)
-used to store binary digit of max
size 255 bytes.
• LONG RAW
-in this data type, it is possible to
store binary data upto 2GB
Object Type
• BLOB
(Binary Large Object)
-this is used for storing binary
data of very large size.
-data stored like images and
videos.
-max size 4GB
• CLOB
(Character Large Object)
-this data type is used to store
very large character object.
-data stored like text document.
-max size 4GB.
*In one table, more than one “lob”
type data type can be stored.

CREATE AND INSERT
(basic)
 CREATE TABLE <table_name>(<column_name>
<data_type>, <column_name> <data_type>,
<column_name> <data_type>);
 DESC <table_name>;
 INSERT INTO <table_name> VALUES (‘<value>’, ’<value>’ ,
’<value>’);
 INSERT INTO <table_name> VALUES (‘&<value>’,
‘&<value>’, ‘&<value>’);

SELECT and UPDATE and
DELETE
 SELECT * FROM <table_name>;
 SELECT <column_name>,<column_name> FROM
<table_name>;
 SELECT * FROM <table_name> WHERE <column_name> =
‘<value>’;
 UPDATE <table_name> SET <column_name> = ‘<value>’;
 UPDATE <table_name> SET <column_name>=‘<value>’
WHERE <condition>;
 DELETE FROM <table_name>;
 DELETE FROM <table_name> WHERE <condition>;

ALTER and DROP
 ALTER TABLE <table_name> ADD (<column_name>
<data_type>(size));
 ALTER TABLE <table_name> DROP COLUMN
<column_name>;
 ALTER TABLE <table_name> MODIFY(<column_name>
<data_type>(size));
 DROP TABLE <table_name>;

DISTINCT and ORDER BY
 SELECT DISTINCT <column_name> FROM <table_name>;
 SELECT DISTINCT * FROM <table_name>;
 SELECT * FROM <table_name> ORDER BY
<column_name>;
 SELECT * FROM <table_name> ORDER BY
<column_name> DESC;

CREATE and INSERT using
previous table.
 CREATE TABLE <table_name a> (<column_name a>, <column_name
a>,…) AS SELECT <column_name b>, <column_name b>,… FROM
<table_name b>;
 CREATE TABLE <table_name a> (<column_name a>, <column_name
a>,…) AS SELECT <column_name b>, <column_name b>,… FROM
<table_name b> WHERE <any_false_condition>;
The above query will create a new table same as <table_name b> but with
no records. This is because the condition can never be fulfilled.
 INSERT INTO <table_name b> SELECT <column_name>,
<column_name>,… FROM <table_name a>;
 INSERT INTO <table_name b> SELECT <column_name a>,
<column_name a>,… FROM <table_name a> WHERE <condition>;

RENAME & VIEW TABLES
 RENAME <table_name a> TO <table_nameb>;
 SELECT * FROM TAB;

PRIMARY KEY and
COMPOSITE KEY
To identify each row uniquely in a table in RDBMS, the concept of primary key is developed.
If it is not possible to identify data uniquely based on single column, PRIMARY KEY is
applied on multiple column and that thing is known as COMPOSITE KEY.
It is applied on a particular column.
• CREATE TABLE <table_name> (<column_1> <data_type>(size) PRIMARY KEY,
<column_2> <data_type>(size), <column_3> <data_type> (size));
Column 1 has PRIMARY KEY CONSTRAINT.
• CREATE TABLE <table_name> (<col_1> <data_type>(size), <col_2>
<data_type>(size), <col_3> <data_type>(size) , PRIMARY KEY (col_1,col_2,col_3));
col_1,col_2,col_3 together have PRIMARY KEY CONSTRAINT on them.

AUTO INCREMENT
-to set auto increment in oracle. We have to create SEQUENCE
• CREATE SEQUENCE <name>
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;
-now when we insert a value to a primary key column, we will use this
sequence object to insert our new values.
• INSERT INTO <table_name> (<column_name>, <column_name>,
<column_name>) values(<name>.nextval, <value>, <value>);
-<name>.nextval will return the next number in SEQUENCE.

FOREIGN KEY
<table_name a> - Detail Table or Foreign Table.
-when a table is created and FK is described in it, that table is known as Detail Table to
the table where this FK is PK to that table.
<table_name b> - Master Table or Primary Table.
-the actual table whose PK is being described in other table as FK.
• CREATE TABLE <table_name a> (
<col_1> <data_type>(size) PRIMARY KEY,
<col_2> <data_type>(size) REFERENCES <table_name b> [(<column_name>)],
<col_3> <data_type>(size) ) ;
-oracle automatically associates <table_name b>’s PK to <col_2> and described
<col_2> as FK, if we don’t mention <column_name> after “REFERENCE
<table_name>” .
 CREATE TABLE <table_name a>(
<col_1> <data_type>(size) PRIMARY KEY,
<col_2> <data_type>(size)
CONSTRAINT <constraint_name> FOREIGN KEY(col_2)
REFERENCES <table_name b>(<column_name>)
);

 [CONSTRAINT [symbol]] FOREIGN KEY [index_name]
(index_col_name, ...) REFERENCES tbl_name
(index_col_name,...) [ON DELETE reference_option] [ON UPDATE
reference_option]
-reference_option: RESTRICT | CASCADE | SET NULL | NO
ACTION

 CREATE TABLE <table_name a> (<col_1> <data_type>(size) PRIMARY KEY,
<col_2> <data_type>(size), <col_3> <data_type>(size), FOREIGN KEY(col_2)
REFERENCES <table_name b>(<column_name>) );
REFERENCES <table_name b>(<column_name>) ) ON DELETE CASCADE;
- “ON DELETE CASCADE” will delete the associated record from <table_name
a> if any record is deleted in the Master Table or <table_name b>.
REFERENCES <table_name b>(<column_name>) ) ON DELETE SET NULL;
- “ON DELETE SET NULL” will set NULL in <table_name a> at the places
where the record is associated to the Master Table or <table_name b>, if the
record is deleted from master table.

UNIQUE KEY
- UK constraint is similar to PK.
-if we apply UK constraint on any column that column can store NULL
values in them, this thing is not possible with PK contraint.
-a column with UK constraint on it can have multiple NULL value, but when
there is actual value stored, no two values can be similar.
• CREATE TABLE <table_name> (
<col 1> <data_type> UNIQUE ,
<col 2> <data_type>,
<col 3> <data_type> );
• CREATE TABLE <table_name> (
<col 1> <data_type> ,
<col 2> <data_type>,
<col 3> <data_type> ,
UNIQUE(col 1));

Business Rule Constraint i.e.
CHECK Constraint
 CREATE TABLE <table_name> (
<col 1> <data_type>(size),
<col 2> <data_type>(size),
<col 3> <data_type>(size) CHECK(<col 3> == 2000),
CHECK(<col 1> LIKE ‘E%’)
);
-in the above query the CHECK constraint is applied on <col 1> & <col
3>
- in <col 1>, it will check if the value which is being inserted, starts from
‘E’ or not.
- in <col 3>, it will check if the value which is being inserted, equals to
‘2000’ or not.
Syntax :
CHECK(<logical_expression>)

Defining Integrity Constraints by
ALTER command
 ALTER TABLE <table_name a> ADD FOREIGN
KEY(<col_name>) REFERENCES <table_name
b>(<col_name>);
 ALTER TABLE <table_name> ADD PRIMARY
KEY(<col_name>);
 ALTER TABLE <table_name> DROP PRIMARY KEY;

NOT NULL and DEFAULT
 CREATE TABLE <table_name>(
<col 1> <data_type>(size) PRIMARY KEY,
<col 2> <data_type>(size) NOT NULL
);
-the insert query wont execute, if there is no data for <col 2>.
 CREATE TABLE <table_name>(
<col 1> <data_type>(size) PRIMARY KEY,
<col 2> <data_type>(size) DEFAULT <value>
);
-if value is string, wrap it in single quotes.
-if number no need to wrap it.

USER_CONTRAINTS table
 DESC USER_CONSTRAINTS;
 SELECT <column_name> FROM
USER_CONSTRAINTS WHERE
TABLE_NAME =‘<table_name>’ ;

Operators
Arithmetic Comparison
 ‘+’ : Addition
 ‘-’ : Subtraction
 ‘*’ : Multiplication
 ‘/’ : Division
 ‘<’ : Is less than
 ‘>’ : Is greater than
 ‘<=’ : Is less than or equal to
 ‘>=’ : Is greater than or equal
to
 ‘=’ : Is equal to
 ‘!=’ : is NOT equal to

Logical Operators
 AND : Logical AND Operator.
 OR : Logical OR Operator.
 NOT : Logical NOT Operator.
examples:
AND
SELECT * FROM EMPLOYEES WHERE
SALARY > 10000 AND SALARY < 25000;
OR
SELECT * FROM SUBJECTS WHERE
NAME = ‘java’ AND NAME < ‘oracle’ ;
NOT
SELECT * FROM EMPLOYEE WHERE
NOT(SALARY > 25000)

Using AND and OR together
 SELECT * FROM EMPLOYEE
WHERE
salary > 25000 AND ( designation= ‘mngr’ OR designation=
‘sec’ );

Range Searching
 SELECT * FROM <table_name>
WHERE <col_name> BETWEEN ‘<value 1>’ AND ‘<value
2>’ ;
- in the output, the tuple(row) with <value 1> and <value 2> will
be included.

Pattern Matching
LIKE Predicate IN and NOT IN Predicate
WHERE <col_name> LIKE
‘E%’;
WHERE <col_name> LIKE
‘%E’;
Assume <col_name> = ‘name’
- when the above query is executed
the output will show all the records
whose ‘name’ are starting with the
letter ‘E’ or ending with letter ‘E’ in
the second query.
WHERE <col_name> IN (‘<value>’);
- the braces after IN can hold multiple
value each of which is separated by
comma.
- the output will contain all records(rows)
where the values of <col_name>
matches to <value>.
WHERE <col_name> NOT IN
(‘<value>’);
-the exact opposite of above query will
happen in this query.

Renaming Columns and Tables
Column Alias Table Alias
 SELECT last_name AS FAMILY,
first_name FROM persons;
-output
FAMILY FIRST_NAME
Jha prakhar
Soni rohit
Yadav ankit
Patel sachin
 SELECT * FROM
<table_name> “<table
_alias>” ;

DUAL Table in Oracle
-we use SELECT command to retrieve output from a table, and
it is compulsory to write a table name with it. But some time
when we need to perform any Arithmetic Calculation or use
some Function, at that point of time we cannot use any table
name because it will return unexpected results, and using
SELECT without table name is incomplete.
For this purpose we use DUAL table.
 DESC DUAL;
 SELECT * FROM DUAL;
 SELECT 2+2 FROM DUAL; output : 4
 SELECT 2*3 FROM DUAL; output: 6
SYSDATE:
 SELECT SYSDATE FROM DUAL; output: current date of your
system

Group Function and Scalar
Functions
-function that works on a set of values are
known as Group Functions or Aggregate
Functions, when we apply any function on
a table's column, it generate output
according to all the values that is selected
by the executed query.
-function that works on single value are
known as scalar functions, they are also
known as ‘single row function’ .

Group Functions
 SELECT AVG(marks) AS “Average Marks” FROM STUDENTS ;
 SELECT COUNT(*) AS “No Of Rows” FROM STUDENTS ;
 SELECT COUNT(name) AS “No Of Rows” FROM STUDENTS ;
 SELECT MAX(marks) AS “Maximum Marks” FROM STUDENTS;
 SELECT MIN(marks) AS “Minimum Marks” FROM STUDENTS;
 SELECT SUM(marks) AS “Sum Of Marks” FROM STUDENTS:
- in above example ‘marks’ & ‘name’ are column in table ‘STUDENTS’ .
- ‘ * ’ used above can be replaced by column names as well.

Scalar Function
Numeric Function
 SELECT ABS(-24) FROM DUAL; output: 24
 SELECT POWER(5,2) FROM DUAL; output: 5*5 = 25
 SELECT ROUND(16.966, 1) FROM DUAL; output: 17.0
 SELECT SQRT(25) FROM DUAL; output: 5
 SELECT EXP(2) FROM DUAL; output: 7.3890561
- this function calculates the value of ‘e’ to the power ‘argument’ where ‘ e = 2.71828183 ’ .
 SELECT GREATEST(12, 20, 40) FROM DUAL; output: 40
 SELECT LEAST(12, 20, 40) FORM DUAL; output: 12;
 SELECT MOD(12,5) FROM DUAL; output: 12 divided by 5 and the answer is 2
 SELECT CEIL(82.2) FROM DUAL; output: 83
 SELECT FLOOR(82.2) FROM DUAL; output: 82

String Function
 SELECT LOWER(‘PRAKHAR’) FROM DUAL; output: prakhar
 SELECT UPPER(‘prakhar’) FROM DUAL; output: PRAKHAR
 SELECT INITCAP(‘pRAKhar’) FROM DUAL; output: Prakhar
 SELECT SUBSTR(‘prakhar’,2,5) FORM DUAL; output: rakha
- in above query, oracle will start reading from 2nd position up till ‘a’ which is at 5th position from there.
 SELECT ASCII(‘A’) FROM DUAL; output: 65
 SELECT INSTR(‘prakhar’, ‘a’) FROM DUAL; output: 3
 SELECT INSTR(‘prakhar’, ‘a’, 1, 2) FROM DUAL; output: 6
-the above query will search for ‘a’ , it will start searching from the first occurrence of ‘a’ and it will search for the
‘a’ at second position.
 SELECT TRANSLATE(‘prakhar’, ‘ar’ , ‘bs’) FROM DUAL; output: psbkhbs
 SELECT LENGTH(‘cow’) “Length Of String” FROM DUAL; output: 3
 SELECT LTRIM(‘prakhar’ , ‘pr’ ) FORM DUAL; output: akhar
-if no argument is passed i.e. in this case ‘pr’ , by default it will remove the white spaces from the starting.
 SELECT RTRIM(‘prakhar’, ‘khar’) FROM DUAL; output: pra

 SELECT TRIM(‘ prakhar ’) AS “TRIM” FROM DUAL; output: prakhar
 SELECT TRIM(LEADING ‘X’ FROM ‘XXXprakharXXX’ ) FROM DUAL;
output: prakharXXX
 SELECT TRIM(TRAILING ‘X’ FROM ‘XXXprakharXXX’ ) FROM DUAL;
output: XXXprakhar
 SELECT TRIM(BOTH ‘X’ FROM ‘XXXprakharXXX’ ) FROM DUAL; output:
prakhar
 SELECT LPAD(‘prakhar’ , 10, ‘*’) FROM DUAL; output: ***prakhar
 SELECT RPAD(‘prakhar’ , 10, ‘*’) FROM DUAL; output: prakhar***

Conversion Function
 SELECT 2 + TO_NUMBER(‘2’) FROM DUAL; output: 4
 SELECT TO_CHAR(12345, ’00,0000’) FROM DUAL; output: 01,2345
- argument passed in the above query ‘12345’ is the input and ’00,0000’ this is the
format we expect in our output.
 SELECT TO_CHAR(SYSDATE, ‘MONTH DD YYYY’) AS “Date” FROM DUAL; output:
March 24 2015
 SELECT TO_CHAR(SYSDATE, ‘MM DD YYYY’) AS “Date” FROM DUAL; output: 03
24 2015
- in the above 2 queries the argument which we have passed the first one represents
input date, and second one is for the format which we expect.
 SELECT TO_DATE(SYSDATE, ‘DD MM YYYY’) “TO DATE” FROM DUAL; output: 24-
03-2015

Date Function
- in oracle there are some function defined, with the help of them we can perform various tasks upon the values
whose type is ‘DATE’.
 SELECT ADD_MONTHS(SYSDATE, 6) “Add Month” FROM DUAL; input: 24-MAR-15 output: 24-SEP-15
- the argument passed in the above question, the first one represents the input date and the second one
represents no. of months to be added to that current date.
 SELECT LAST_DAY(SYSDATE) “Last Day” FROM DUAL; input (SYSDATE): 24-MAR-15 output: 31-MAR-15
 SELECT NEXT_DAY(’24-MAR-15’, ‘monday’) FROM DUAL; output: 30-MAR-15
- the above function needs two arguments first one is the date and second one is day.
- this function helps us to find the date which will occur on the inputted day, and the date will be after ‘24-MAR-15’
i.e. the inputted date in above case.
 SELECT MONTHS_BETWEEN( ‘06-JAN-16’ , ’06-APR-15’) FROM DUAL; output: 1
- the above function requires two arguments which are date, and this function will find out the months between
these two dates.
 SELECT TO_CHAR(SYSDATE, ‘DDTH/MM/YY’) FROM DUAL; output: example - 24TH/MAR/15
 SELECT TO_CHAR(SYSDATE, ‘DDSP/MM/YY’) FROM DUAL; output: example – twenty-four/MAR/15
 SELECT TO_DATE(’24/03/2015’, ‘DD/MM/YYYY’) FROM DUAL; output: 24-MAR-15
- in the above query the first argument is the string date which we want to cast in date formant, the second
argument is to tell the function that in which format we are sending the date.

This is COMPANY table and Grouping
functions are applied on it
COMPANY AMOUNT
Tcs 12000
Tcs 20000
Hp 40000
Hp 30000
TABLE NAME = COMPANY
 SELECT COMPANY, SUM(amount) FROM
COMPANY WHERE COMPANY = ‘Hp’
GROUP BY COMPANY;
- In the above query the table name and the
first column name are both ‘COMPANY’
- The output of the query will be executed in
a manner such that all the rows with the
company name ‘Hp’ will collapse and
become one and all the data in the amount
column against ‘Hp’ will be added together.
 SELECT COMPANY, SUM(amount) FROM
COMPANY GROUP BY COMPANY HAVING
SUM(amount)>4000;
- We use ‘HAVING’ clause in a situation
where we need further filtration on a result.
- In the above query the ‘group by’ clause will
generate a result and the ‘having’ clause will
provide further filtration on it.
output : Hp 70000

Example table to understand joins
employees Table (j.1) orders Table (j.2)
emp_id (pk) emp_name
E01 Pandey sunil
E02 Dubey ajay
E03 Dubey anand
E04 Singh ashwin
prod_id
(pk)
prod_name emp_id
(fk)
234 Printer E01
657 Table E03
865 Chair E03

Inner Join
Inner join is used for handling complex data. When we need to
extract the data from multiple tables then ‘inner join’ keyword is
used.
 SELECT e.emp_name, o.prod_name FROM orders o INNER
JOIN employees e ON e.emp_id = o.emp_id;
-output:
1- pandey sunil printer
2- dubey anand table
3- dubey anand chair
- the above query can also be formed this way.
 SELECT employees.emp_name, orders.prod_name FROM
orders INNER JOIN employees ON employees.emp_id =
orders.emp_id;

Right Join
This join works in a way that, the output of the query with right join will contain all the rows
that are present in the table whose name is written on the right side of this keyword.
 SELECT e.emp_name, o.prod_name FROM orders o RIGHT JOIN employees e ON
e.emp_id = o.emp_id;
-output:
4- singh ashwin
5- dubey ajay
 SELECT employees.emp_name, orders.prod_name FROM orders INNER JOIN
employees ON employees.emp_id = orders.emp_id;

Left Join
This join works in a way that, the output of the query with left join will contain all the rows
that are present in the table whose name is written on the left side of this keyword.
 SELECT e.emp_name, o.prod_name FROM orders o LEFT JOIN employees e ON
e.emp_id = o.emp_id;
-output:
 SELECT employees.emp_name, orders.prod_name FROM orders LEFT JOIN
employees ON employees.emp_id = orders.emp_id;

Self Join table( j.3 )
Id Name Type
1 Teacher 1
2 Student 1 0
3 Student 2 0
- Let this table name be “persons”
- In self join we treat one single
table as two different table.
- All the columns in this table and
all the example tables have data
type VARCHAR2(10).
 SELECT teacher.name “Teacher
Name”, student.name “Student”
FROM persons teacher, person
student where student.type=‘0’
and teacher.type=‘1’;
-output:
Teacher Name Student Name
1 Teacher Student 1
2 Teacher Student 2

Cross Join
Sr_No Course_Name
1 BCA
2 BSC
Table: courses
Sr_no Sub_Name
1 oracle
2 java
Table: subjects
 SELECT c.course_name,
s.subject_name FROM
courses c CROSS JOIN
subjects s;
 SELECT
courses.course_name,
subjects.subject_name
FROM courses CROSS JOIN
subjects;
Output:
1. BSC oracle
2. BSC java
3. BCA oracle
4. BSC java

Sub-Queries
- We will use table ‘j.1’ and table ‘j.2’ to
create a example showing how to use sub
queries.
 SELECT * FROM orders WHERE emp_id
IN (SELECT emp_id FROM employees
WHERE emp_name=‘Pandey sunil’);
output:
234 printer E01

UNION and UNION ALL
- UNION helps us to take out records from multiple tables and join
them.
- The records that are present in the output, there can be multiple
similar records but since we are using ‘UNION’ only single set of the
total records will be displayed or we can say there will be no similar
records in the output.
- Just like UNION, UNION ALL is used the basic difference between
them is that, when we use UNION no duplicate record is displayed.
Well in the case of UNION ALL, all the outputs which are generated
by the individual query are displayed. We will see repetition of
records while using UNION ALL clause.
- Using table (j.1) and (j.2) we will query on these table to understand
‘union’ and ‘union all’ more effectively.

SELECT emp_id FROM employees UNION SELECT emp_id FROM
orders;
SELECT emp_id FROM employees UNION ALL SELECT emp_id
FROM orders;
UNION query output UNION ALL query output
Emp_id
E01
E02
E03
E04
Emp_id
E01
E02
E03
E04
E01
E03
E03

INTERSECT
 SELECT emp_id FROM
employees INTERSECT
SELECT emp_id FROM
orders;
- the only records which
are common in both the
table will be show as the
output of the above
query.
output:
right side.
Emp_id
E01
E03

MINUS
 SELECT emp_id FROM
employees MINUS SELECT
emp_id FROM orders;
- the output of the above
query will contain all the
emp_id’s which are present
in the employees table but
not in the orders table.
- if we swap places of both
the table name in the above
query the output will have
no records to display,
because order table have
emp_id (1, 3) where as in
employees (1,2,3,4).
Emp_id
E02
e04

VIEWS
 They are used for security purposes, so that each column of a
table can only be seen by those who are authorized to see it.
 If for each user we define part-of a particular table so that he
can see only those columns which they are allowed to, the
redundancy will increase and this sort of approach is inefficient,
but have the capability to provide security.
 View don’t have data stored in them. They read the table and
also read there own implementation so as to know, what are all
the columns the need to show to the user.
 We can use views as if they are tables, we can perform CRUD
queries.
 Views are of 2 types READ-ONLY and UPDATABLE.

CREATE , SELECT and INSERT
 CREATE VIEW <view_name> AS SELECT <col_name>
“<alias_name>”, <col_name 1> “<alias_name 1>” ,….FROM
<table_name>;
 SELECT <alias_name>, <alias_name1>, … FROM
<view_name>;
 INSERT INTO <view_name> values (‘<value>’, ‘<value>’);
 UPDATE <view_name> SET <alias_name> = ‘<value>’ WHERE
<alias_name?> = ‘<value>’;
 DELETE FROM <view_name> WHERE
<alias_name?>=‘<value>’;
 DROP VIEW <view_name>;

Limitations (updatable view)
- Aggregate functions cannot be used.
- DISTINCT, HAVING, GROUP BY clause cannot be used.
- Sub queries cannot be used.
- UNION, INTERSECT and MINUS cannot be used.
- Constant, Strings and Expressions.
If one view is defined by another the other view must be
updatable.

Oracle basic queries

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