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[[[server.][database].][schema].]database_object Each of these identifiers must comply with the rules described in the previous section. Server, database, and schema are often referred to as database object qualifiers. The complete name of the object is often referred to as the fully qualified name, or four-part name. Schema is a part of the name that is used to logically group database objects. You can also think of them as a namespace. Two database objects can have the same name as long as they belong to different namespaces. SQL Server 2005 databases by default have a couple of namespaces: dbo (as default schema), INFORMATION_SCHEMA (defined by SQL-92 Standard for system views that provide metadata information), sys (for system tables and views), and guest. In SQL Server 2005, a user can create database objects that belong to any schema. If a user does not specify the schema, SQL Server 2005 will make it part of the default dbo schema. It is possible to define another schema and assign it as a default schema to any user. You can find more details about schemas in BOL.
NOTE When you are referencing the object, if you do not specify the name of the schema, SQL Server will first try to find the object in the sys schema. If such an object does not exist, SQL Server will try to locate it in the schema named the same as the user. If it does not exist there either, SQL Server will attempt to find it in the dbo schema. For example, to resolve the stored procedure name ap_Eq_List specified by using dsunderic without a schema name, SQL Server 2005 will try to find it as:
TIP
Server and database are (naturally) the names of the server and the database in which the object is stored. ap_Eq_List dbo.ap_Eq_List Asset5.dbo.ap_Eq_List Asset5..ap_Eq_List SQLBox.Asset5..ap_Eq_List SQLBox...ap_Eq_List SQLBox..dbo.ap_Eq_List
NOTE But the real advantage of a schema is that you can use it to group database objects such as those in the Object Browser (see Figure 3-1).
 The previous tip is from "15 tips in 15 minutes: Basic Transact-SQL Programming Constructs," excerpted from Chapter 3, of the book "Microsoft SQL Server 2005 Stored Procedure Programming in T-SQL & .NET" by Dejan Sunderic, courtesy of McGraw-Hill Publishing.
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