SQL Server表架构名称

Question

I have some questions about the schema in a table.

Sometime when you create a table the default schema is dbo.TableName. Is the dbo the default schema name? I believe you can change or specify the schema when creating a table right, because there are tables that have different schema like: Sales.Tablename or Users.Roles, etc. I believe the purpose of a schema is to make a difference between tables or something like that? Something like a namespace within a C# class. Is it possible to have two tables with same name but a different schema, like: Sales.Users, Marketing.Users ?

Answer 1

1. dbo is the default schema. You can change the default schema for each sql-login. If you accidentally create a table in the wrong schema, you can move it:

   -- Moving Peter table from Sales schema to Orders schema

   ALTER SCHEMA Orders TRANSFER Sales.peter

2. You can specify which schema to create the table in by specifying it before the table name:

   CREATE TABLE Sales.Users(id int);

3. One of the purposes of schemas is to create logical groups of tables, just like namespaces in C#. They are also useful for controlling permissions and more.

4. Yes, table names only need to be unique within each schema..

Answer 2

Sometime when you create a table the default schema is dbo.TableName. Is the dbo the default schema name?

Why do you ask? It is quite obvious that dbo is the default schame name if you get it as default, or? On top it is the only usable schema a new database has.

I believe you can change or specify the schema when creating a table right,

What sense would multiple schemata have if you could not use them? And as the create table syntax clearly states you can specify a schema.

I believe the purpose of a schema is to make a difference between tables or something like that? Something like a namespace within a C# class.

That pretty much sums it up.

Is it possible to have two tables with same name but a different schema,

What about you spend 10 seconds to try it out? Are you challenged by he concept of trying something totally simplistic out? And the answer is yes. object names have to be unique - within their schema.