DDL stands for “ data definition language”. It is the subset of SQL commands used to create,...
-
Upload
brianna-rodgers -
Category
Documents
-
view
215 -
download
1
Transcript of DDL stands for “ data definition language”. It is the subset of SQL commands used to create,...
Data definition language(DDL) DDL stands for “ data definition
language”. It is the subset of SQL commands used to
create, modify and destroy databases and database objects like –tables , views etc.
A data Definition Language has a pre-defined syntax for describing data .
For example – To built a new table using SQL syntax the CREATE command is used, followed by parameters for the table name and column definition .
The DDL can also define the name of each column and the associated data type.
Once a table is created , it can be modified using the ALTER command .
If the table is no longer needed , the DROPcommand will delete the table.
Some of the comman DDL
statements in oracle include CREATE, ALTER, DROP, RENAME, TRUNCATE etc.
CREATING TABLES
The CREATE TABLE command is used to create tables to store data.
Tables are owned by the user who creates them. The names of tables owned by a given user must be unique . The column names in the table must be unique .
Specifying table name is compulsory while creating a table.
The syntax for the CREATE TABLE statement is :
CREATE TABLE table _name
(column _name1 data type,
Column _name2 data type,
…column _nameN data type);
EXAMPLE:
CREATE TABLE STUDENT _RECORD
( Name varchar2 (20) , Class varchar2 (10), Roll _no number(5), Section char (1), Marks number (5,2) );
Column name Type Size Description
Name Varchar2 20 Name of student
Class Varchar2 10 Class of student
Roll no Number 5 Roll number of student
Section Char 1 Section of student’s class
Marks Number 5,2 Marks obtained by student
STUDENT RECORD
CREATING A TABLE WITH DATA FROM ANOTHER TABLE
A table can be created by using CREATE TABLE statement with data, derived another table .
The syntax is :
CREATE TABLE NEW _TABLE_NAME
[(Column_1, column_2,…. Column_n)] ,
AS SELECT Column _1 , column_2 ,…. Column _n
From OLD_TABLE_NAME ;
FOR EXAMLE
Create a table STUDENT1 from student table having student name and Rollno .
CREATE TABLE STUDENT1 [( NAME , ROLLNO)]AS SELECT NAME , CLASS,
ROLLNO, AGEFROM STUDENT
INSERT STATMENT
It is used to insert new rows/records in a table.
Values can be inserted for all the columns or for selected columns of the table.
We can insert data values into a table through different ways:
Inserting the data direct to the table.
Inserting the data to a table through a select statement.
The syntax for INSERT statement is:
INSERT INTO TABLE_NAME VALUES(value 1,value 2,value 3,
…….value n);
Example: class is a table name.Insert into class values(‘ram’, 20,
’bca’);
Following statements would create 4 records in CUSTOMERS table:
INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY) VALUES (1, 'Ramesh', 32, 'Ahmedabad', 2000.00 ); INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY) VALUES (2, 'Khilan', 25, 'Delhi', 1500.00 ); INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY) VALUES (3, 'kaushik', 23, 'Kota', 2000.00 ); INSERT INTO CUSTOMERS (ID,NAME,AGE,ADDRESS,SALARY) VALUES (4, 'Chaitali', 25, 'Mumbai', 6500.00 );
ID NAME AGE ADDRESS SALARY
1 RAMESH 32 AHEMDABAD 2000.00
2 KHILAN 25 DELHI 1500.00
3 KAUSHIK 23 KOTA 2000.00
4 CHAITALI 25 MUMBAI 6500.00
UPDATE STATEMENT
To update or modify the exiting rows in a table.
It modifies specific rows if the WHERE clause is specified.
We can use WHERE clause with UPDATE query to update selected rows otherwise all the rows would be affected.
The basic syntax of UPDATE query with WHERE clause is as follows:
UPDATE table_nameSET column1 = value1, column2 =
value2...., column N = value NWHERE [condition];
Example: UPDATE EMP SET COMM=500;EMP is the table name.
Consider the CUSTOMERS table having the following records:
ID NAME AGE ADDRESS SALARY
1 RAMESH 32 AHEMDABAD 2000.00
2 KHILAN 25 DELHI 1500.00
3 KAUSHIK 23 KOTA 2000.00
4 CHAITALI 25 MUMBAI 6500.00
Following is an example, which would update ADDRESS for a customer whose ID is 6:
SQL> UPDATE CUSTOMERSSET ADDRESS = 'Pune'WHERE ID = 4;
Now, CUSTOMERS table would have the following records:
ID NAME AGE ADDRESS SALARY
1 RAMESH 32 AHEMDABAD 2000.00
2 KHILAN 25 DELHI 1500.00
3 KAUSHIK 23 KOTA 2000.00
4 CHAITALI 25 PUNE 6500.00
DELETE STATEMENT
It is used to delete rows from a table.
To delete rows from a table, table must be in your schema.
We can use WHERE clause with DELETE query to delete selected rows, otherwise all the records would be deleted.
The basic syntax of DELETE query with WHERE clause is as follows:
DELETE FROM table_nameWHERE [condition];Example:DELETE FROM EMPWHERE JOB=‘ CLERK’;EMP is the table name.
Consider the CUSTOMERS table having the following records:
ID NAME AGE ADDRESS SALARY
1 RAMESH 32 AHEMDABAD 2000.00
2 KAUSHIK 25 DELHI 1500.00
3 KHILAN 23 KOTA 2000.00
4 CHAITALI 25 MUMBAI 6500.00
Following is an example, which would DELETE a customer, whose ID is 6:
SQL> DELETE FROM CUSTOMERSWHERE ID = 4;
Now, CUSTOMERS table would have the following records:
ID NAME AGE ADDRESS SALARY
1 RAMESH 32 AHEMDABAD 2000.00
2 KAUSHIK 25 DELHI 1500.00
3 KHILAN 23 KOTA 2000.00