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SQL TABLE Keyword


CREATE TABLE

The CREATE TABLE command creates a new table in the database.

The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City:

Example

CREATE TABLE Persons (
    PersonID int,
    LastName varchar(255),
    FirstName varchar(255),
    Address varchar(255),
    City varchar(255)
);

CREATE TABLE Using Another Table

A copy of an existing table can also be created using CREATE TABLE.

The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table): 

Example

CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;

ALTER TABLE

The ALTER TABLE command adds, deletes, or modifies columns in a table.

The ALTER TABLE command also adds and deletes various constraints in a table.

The following SQL adds an "Email" column to the "Customers" table:

Example

ALTER TABLE Customers
ADD Email varchar(255);

The following SQL deletes the "Email" column from the "Customers" table:

Example

ALTER TABLE Customers
DROP COLUMN Email;

DROP TABLE

The DROP TABLE command deletes a table in the database.

The following SQL deletes the table "Shippers":

Example

DROP TABLE Shippers;

Note: Be careful before deleting a table. Deleting a table results in loss of all information stored in the table!


TRUNCATE TABLE

The TRUNCATE TABLE command deletes the data inside a table, but not the table itself.

The following SQL truncates the table "Categories": 

Example

TRUNCATE TABLE Categories;