Drupal Schema module from existing database to hook_schema

Drupal Schema module

The Schema API allows the module to declare a database in the Form of a structured array (similar to the Form API), and provides API functions for creating, deleting, and modifying data tables, columns, keys, and indexes.

The Schema module provides some functions other than the Schema API of the Drupal core architecture. Currently, this includes:

Schema document: an embedded document that displays Schema in hyperlink form is used to explain what each data table and field is doing.
Schema structure generation: the Schema module can check the real-time database and create the Schema API data structure of all tables in the matched real-time database.
Schema comparison: the Schema module compares the real-time database structure with the schema structure defined by all enabled modules to report any lost or incorrect tables.
MySQL considerations: the Schema module requires MySQL version 5 or later. MySQL versions earlier than MySQL do not support the Schema module to check the INFORMATION_SCHEMA database in the database.

Type	Size	MySQL type & size/range
Serial	Tiny	Tinyint, 1 B
Serial	Small	Smallint, 2 B
Serial	Medium	Mediumint, 3 B
Serial	Big	Bigint, 8 B
Serial	Normal	Int, 4 B
Int	Tiny	Tinyint, 1 B
Int	Small	Smallint, 2 B
Int	Medium	Mediumint, 3 B
Int	Big	Bigint, 8 B
Int	Normal	Int, 4 B
Float	Tiny	Float, 4 B
Float	Small	Float, 4 B
Float	Medium	Float, 4 B
Float	Big	Double, 8 B
Float	Normal	Float, 4 B
Numeric	Normal	Numeric, 65 digits
Varchar	Normal	Varchar, 255 B (D6) or 64 KB (D7 and later)1
Char	Normal	Char, 255 B
Text	Tiny	Tinytext, 256 B
Text	Small	Tinytext, 256 B
Text	Medium	Mediumtext, 16 MB
Text	Big	Longtext, 4 GB
Text	Normal	Text, 16 KB
Blob	Big	Longblob, 4 GB
Blob	Normal	Blob, 16 KB

Download the Schema module:

Http://drupal.org/project/schema

Original article from: blog.lixiphp.com