Two meanings of database schema ~ ~

1, the database schema has two meanings, one is a conceptual schema, refers to a set of DDL statements, the statement set is a complete description of the structure of the database. There is also a physical Schema, which refers to a namespace in a database that contains a set of named objects, such as tables, views, and stored procedures. The physical schema can be created, updated, and modified through standard SQL statements. For example, the following SQL statement creates two physical schemas:

Create schema Schema_a;
CREATE TABLE schema_a.customers (ID int not null,......);

Create schema Schema_b;
CREATE TABLE schema_b.customers (ID int not null,......);

2, simply say: is a database user owned database objects.

3, database: Refers to say MySQL (or Oracle, etc.)

Schema: refers to that when I create database CAICECLB, CAICECLB is a schema

Catalog: Refers to all of the database directories, as shown, will be MySQL original (Mysql,infomation_schema) and later a new set of database.

The above is excerpted from http://www.360doc.com/content/12/0424/11/3303212_206103980.shtml

Two meanings of database schema ~ ~