2. Table Basic

§ Tables are divided into columns and rows.

§ Defining datatype for each column

Creating Table

Syntax

CREATETABLEtable_name(

   column1 datatype,

   column2 datatype,

   column3 datatype,

.....

columnN datatype,

PRIMARYKEY ( one or more columns)

);

§ The unique name or identifier for the table follows the CREATE TABLE statement.

§ Then in brackets comes the list defining each column in the table and what sort of data type it is.

Example

CREATETABLE CUSTOMERS(

   ID   INTNOTNULL,

   NAME VARCHAR (20)NOTNULL,

   AGE INTNOTNULL,

ADDRESSCHAR (25),

   SALARY   DECIMAL (18, 2),

                PRIMARYKEY (ID)

);

Modifying Table

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

Syntax

ALTERTABLEtable_name

ADDcolumn_name datatype

Syntax for modifying

ALTERTABLEtable_name

ALTERCOLUMNcolumn_name datatype

Syntax for deleting

ALTERTABLEtable_name

DROPCOLUMNcolumn_name

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