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One Shot

Creating & using Databadse

Database is a memory location where all tables will get placed.

Creating Database

                     create database databasename

using database

                    use databasename

SQL

• It Stands for Structured Query Language.
• It is a ANSI standard which provides to creating and managing the database objects.
• It could be classified into following categories-
  • DDL
  • DML
  • DQL

DDL

• DDL stands for data definition language, it is used for creating a database object like table. These are-
      1. create
      2. alter
      3. drop

create 

This command is used for creating a table.
Syntax
    create table tablename(fieldname datatype(size),......);

Data Types

•  varchar
•  numeric
•  int
•  date

Example

Table Name :

       emp

Fields

1. eid
2. ename
3. esalary
4. edesig

alter command

This command modifying the structure of a table.

Syntax-1: Adding a new column

        alter table tablename add columnname datatype(size);

Example
             Add a new column named as edeptno & ephno

alter command 

Syntax-2: Modifying an existing column

alter table tablename modify columnname datatype(size);
            

Example

      set the size of ename field as 120 characters
        

alter command 

Syntax-3: Deleting an Existing Column

alter table tablename drop column columnname

Example
            delete the column named as ephno
        

alter command 

Syntax-4: Renaming an existing Column.

alter table tablename change column oldcolumnname  newcolumnname datatype(size)
         

Example

change the name of column esalary to esal

drop command

This command is used for deleting a table.

Syntax

           drop table tablename

DML Statements

These commands are used for manipulating the content of a table. They are-

1.  insert    
2.  delete
3.  update

Insert Command

This command is used for inserting the data into a table.

Syntax-1: inserting data in all the fields
         

     insert into tablename values(value1,value2,...)
    

Insert Command

Syntax-2: inserting data in particular the fields
            

Syntax

insert into tablename(field1,field2,..) values(value1,value2,...);
    

Delete Command

This command is used for deleting the content of a table.

Syntax

        delete from tablename [where condition]

Update Command

This command is used for modifying the content of a table.

Syntax

update tablename set columnname=value [where condition]

Data Query Language

select command is known as Data Query Language.

Syntax-1:

         Select *|fieldname from tablename

Syntax-2:

        select *|fieldname from tablename where condition.