Friday, August 5, 2011

Oracle SQL Basic Queries

SQL is divided into the following
Ø Data Definition Language (DDL)
Ø Data Manipulation Language (DML)
Ø Data Retrieval Language (DRL)
Ø Transaction Control Language (TCL)
Ø Data Control Language (DCL)
DDL -- create, alter, droap, truncate, rename
DML -- insert, update, delete
DRL -- select
TCL -- commit, rollback, savepoint
DCL -- grant, revoke

CREATE TABLE SYNTAX
Create table <table_name> (col1 datatype1, col2 datatype2 …coln datatypen);
Ex:
SQL> create table student (no number (2), name varchar (10), marks number (3));

INSERT
This will be used to insert the records into table.
We have two methods to insert.
Ø By value method
Ø By address method

a) USING VALUE METHOD
Syntax:
insert into <table_name) values (value1, value2, value3 …. Valuen);
Ex:
SQL> insert into student values (1, ’sudha’, 100);
SQL> insert into student values (2, ’saketh’, 200);

To insert a new record again you have to type entire insert command, if there are lot of
records this will be difficult.
This will be avoided by using address method.

b) USING ADDRESS METHOD
Syntax:
insert into <table_name) values (&col1, &col2, &col3 …. &coln);
This will prompt you for the values but for every insert you have to use forward slash.
Ex:
SQL> insert into student values (&no, '&name', &marks);
Enter value for no: 1
Enter value for name: Jagan
Enter value for marks: 300
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(1, 'Jagan', 300)
SQL> /
Enter value for no: 2
Enter value for name: Naren
Enter value for marks: 400
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(2, 'Naren', 400)

c) INSERTING DATA INTO SPECIFIED COLUMNS USING VALUE METHOD
Syntax:
insert into <table_name)(col1, col2, col3 … Coln) values (value1, value2, value3 ….
Valuen);
Ex:
SQL> insert into student (no, name) values (3, ’Ramesh’);
SQL> insert into student (no, name) values (4, ’Madhu’);

d) INSERTING DATA INTO SPECIFIED COLUMNS USING ADDRESS METHOD
Syntax:
insert into <table_name)(col1, col2, col3 … coln) values (&col1, &col2, &col3 …. &coln);
This will prompt you for the values but for every insert you have to use forward slash.
Ex:
SQL> insert into student (no, name) values (&no, '&name');
Enter value for no: 5
Enter value for name: Visu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(5, 'Visu')
SQL> /
Enter value for no: 6
Enter value for name: Rattu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(6, 'Rattu')

SELECTING DATA
Syntax:
Select * from <table_name>; -- here * indicates all columns
or
Select col1, col2, … coln from <table_name>;
Ex:
SQL> select * from student;
NO NAME MARKS
--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select no, name, marks from student;
NO NAME MARKS
--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select no, name from student;
NO NAME
--- -------
1 Sudha
2 Saketh
1 Jagan
2 Naren
3 Ramesh
4 Madhu
5 Visu
6 Rattu

CONDITIONAL SELECTIONS AND OPERATORS
We have two clauses used in this
Ø Where
Ø Order by

USING WHERE
Syntax:
select * from <table_name> where <condition>;
the following are the different types of operators used in where clause.
v Arithmetic operators
v Comparison operators
v Logical operators
v Arithmetic operators -- highest precedence
+, -, *, /
v Comparison operators
Ø =, !=, >, <, >=, <=, <>
Ø between, not between
Ø in, not in
Ø null, not null
Ø like
v Logical operators
Ø And
Ø Or -- lowest precedence
Ø not
a) USING =, >, <, >=, <=, !=, <>
Ex:
SQL> select * from student where no = 2;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
2 Naren 400

b) USING AND
This will gives the output when all the conditions become true.
Syntax:
select * from <table_name> where <condition1> and <condition2> and .. <conditionn>;
Ex:
SQL> select * from student where no = 2 and marks >= 200;
NO NAME MARKS
--- ------- --------
2 Saketh 200
2 Naren 400

c) USING OR
This will gives the output when either of the conditions become true.
Syntax:
select * from <table_name> where <condition1> and <condition2> or .. <conditionn>;
Ex:
SQL> select * from student where no = 2 or marks >= 200;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400

d) USING BETWEEN
This will gives the output based on the column and its lower bound, upperbound.
Syntax:
select * from <table_name> where <col> between <lower bound> and <upper bound>;
Ex:
SQL> select * from student where marks between 200 and 400;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400

e) USING NOT BETWEEN
This will gives the output based on the column which values are not in its lower bound,
upperbound.
Syntax:
select * from <table_name> where <col> not between <lower bound> and <upper bound>;
Ex:
SQL> select * from student where marks not between 200 and 400;
NO NAME MARKS
--- ------- ---------
1 Sudha 100

f) USING IN
This will gives the output based on the column and its list of values specified.
Syntax:
select * from <table_name> where <col> in ( value1, value2, value3 … valuen);
Ex:
SQL> select * from student where no in (1, 2, 3);
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh

g) USING NOT IN
This will gives the output based on the column which values are not in the list of values
specified.
Syntax:
select * from <table_name> where <col> not in ( value1, value2, value3 … valuen);
Ex:
SQL> select * from student where no not in (1, 2, 3);
NO NAME MARKS
--- ------- ---------
4 Madhu
5 Visu
6 Rattu

h) USING NULL
This will gives the output based on the null values in the specified column.
Syntax:
select * from <table_name> where <col> is null;
Ex:
SQL> select * from student where marks is null;
NO NAME MARKS
--- ------- ---------
3 Ramesh
4 Madhu
5 Visu
6 Rattu

i) USING NOT NULL
This will gives the output based on the not null values in the specified column.
Syntax:
select * from <table_name> where <col> is not null;
Ex:
SQL> select * from student where marks is not null;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400

j) USING LIKE
This will be used to search through the rows of database column based on the pattern you
specify.
Syntax:
select * from <table_name> where <col> like <pattern>;
Ex:
i) This will give the rows whose marks are 100.
SQL> select * from student where marks like 100;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
ii) This will give the rows whose name start with ‘S’.
SQL> select * from student where name like 'S%';
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
iii) This will give the rows whose name ends with ‘h’.
SQL> select * from student where name like '%h';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh
iV) This will give the rows whose name’s second letter start with ‘a’.
SQL> select * from student where name like '_a%';
NO NAME MARKS
--- ------- --------
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
6 Rattu
V) This will give the rows whose name’s third letter start with ‘d’.
SQL> select * from student where name like '__d%';
NO NAME MARKS
--- ------- ---------
1 Sudha 100
4 Madhu
Vi) This will give the rows whose name’s second letter start with ‘t’ from ending.
SQL> select * from student where name like '%_t%';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
6 Rattu
Vii) This will give the rows whose name’s third letter start with ‘e’ from ending.
SQL> select * from student where name like '%e__%';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh
Viii) This will give the rows whose name cotains 2 a’s.
SQL> select * from student where name like '%a% a %';
NO NAME MARKS
--- ------- ----------
1 Jagan 300
* You have to specify the patterns in like using underscore ( _ ).

USING ORDER BY
This will be used to ordering the columns data (ascending or descending).
Syntax:
Select * from <table_name> order by <col> desc;
By default oracle will use ascending order.
If you want output in descending order you have to use desc keyword after the column.
Ex:
SQL> select * from student order by no;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
1 Jagan 300
2 Saketh 200
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select * from student order by no desc;
NO NAME MARKS
--- ------- ---------
6 Rattu
5 Visu
4 Madhu
3 Ramesh
2 Saketh 200
2 Naren 400
1 Sudha 100
1 Jagan 300
USING DML

USING UPDATE
This can be used to modify the table data.
Syntax: Update <table_name> set <col1> = value1, <col2> = value2 where <condition>;
Ex: SQL> update student set marks = 500;
If you are not specifying any condition this will update entire table.
SQL> update student set marks = 500 where no = 2;
SQL> update student set marks = 500, name = 'Venu' where no = 1;

USING DELETE
This can be used to delete the table data temporarily.
Syntax: Delete <table_name> where <condition>;
Ex: SQL> delete student;
If you are not specifying any condition this will delete entire table.
SQL> delete student where no = 2;

USING DDL
USING ALTER
This can be used to add or remove columns and to modify the precision of the datatype.

a) ADDING COLUMN
Syntax: alter table <table_name> add <col datatype>;
Ex: SQL> alter table student add sdob date;

b) REMOVING COLUMN
Syntax: alter table <table_name> droap <col datatype>;
Ex: SQL> alter table student droap column sdob;

c) INCREASING OR DECREASING PRECISION OF A COLUMN
Syntax: alter table <table_name> modify <col datatype>;
Ex: SQL> alter table student modify marks number(5);
* To decrease precision the column should be empty.

d) MAKING COLUMN UNUSED
Syntax: alter table <table_name> set unused column <col>;
Ex: SQL> alter table student set unused column marks;
Even though the column is unused still it will occupy memory.

d) droapPING UNUSED COLUMNS
Syntax: alter table <table_name> droap unused columns;
Ex: SQL> alter table student droap unused columns;
* You can not droap individual unused columns of a table.

e) RENAMING COLUMN
Syntax: alter table <table_name> rename column <old_col_name> to <new_col_name>;
Ex: SQL> alter table student rename column marks to smarks;

USING TRUNCATE
This can be used to delete the entire table data permanently.
Syntax: truncate table <table_name>;
Ex: SQL> truncate table student;

USING droap
This will be used to droap the database object;
Syntax: droap table <table_name>;
Ex: SQL> droap table student;

USING RENAME
This will be used to rename the database object;
Syntax: rename table_name> to <new_table_name>;
Ex: SQL> rename student to stud;



USING ALIASES
CREATE WITH SELECT
We can create a table using existing table [along with data].
Syntax: Create table <new_table_name> [col1, col2, col3 ... coln] as select * from
<old_table_name>;
Ex: SQL> create table student1 as select * from student;
Creating table with your own column names.
SQL> create table student2(sno, sname, smarks) as select * from student;
Creating table with specified columns.
SQL> create table student3 as select no,name from student;
Creating table with out table data.
SQL> create table student2(sno, sname, smarks) as select * from student where 1 = 2;
In the above where clause give any condition which does not satisfy.

INSERT WITH SELECT
Using this we can insert existing table data to a another table in a single trip. But the table structure should be same.
Syntax: Insert into <table1> select * from <table2>;
Ex: SQL> insert into student1 select * from student;
Inserting data into specified columns
SQL> insert into student1(no, name) select no, name from student;

COLUMN ALIASES
Syntax: Select from _name>;
Ex: SQL> select no sno from student; or
SQL> select no “sno” from student;

TABLE ALIASES
If you are using table aliases you can use dot method to the columns.
Syntax: Select <alias_name>.<col1>, <alias_name>.<col2> … <alias_name>.<coln> from
<table_name> <alias_name>;
Ex: SQL> select s.no, s.name from student s;

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