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W3schools - SQL_DDL

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CREATE DATABASE

Is used to create a new SQL database

CREATE DATABASE databasename;
-- Make sure you have admin privilege before creating any database.

DROP DATABASE

Is used to drop an existing SQL database

DROP DATABASE databasename;

BACKUP DATABASE

Is used in SQL Server to create a full back up of an existing SQL database

Always back up the database to a different drive than the actual database

  • Then, if you get a disk crash, you will not lose your backup file along with the database
BACKUP DATABASE databasename
TO DISK = ‘filepath’;
-- A differential back up only backs up the parts of the database that have changed since the last full database backup
BACKUP DATABASE databasename
TO DISK = ‘filepath’
WITH DIFFERENTIAL;

CREATE TABLE

Is used to create a new table in a database

CREATE TABLE table_name(
column1 datatype,
column2 datatype,
….
);
-- Using another table
CREATE TABLE new_table_name AS
SELECT column(s)
FROM existing_table_name
WHERE condition;
-- The column parameters specify the names of the column of the table
-- The datatype parameter specifies the type of data the column can hold

DROP TABLE

Is used to drop an existing table in a database

DROP TABLE table_name;

TRUNCATE TABLE

Is used to delete the data inside a table, but not the table itself

TRUNCATE TABLE table_name;

ALTER TABLE

Is used to add, delete, or modify columns in a existing table

Is also used to add and drop various constraints on an existing table

-- ADD
ALTER TABLE table_name
ADD column_name datatype;
-- DROP
ALTER TABLE table_name
DROP COLUMN column_name;
-- MODIFY
ALTER TABLE table_name
MODIFY column_name datatype;