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;