Default Schemas in SQL Server

Kevin Feasel

2019-06-14

T-SQL

Max Vernon takes us through the order in which SQL Server searches for tables given a single-part name:

Default schemas in SQL Server can be a blessing, since they reduce the need to specify the schema when creating DDL statements in T-SQL. However, relying on the default schema when creating DML statements can be problematic. A recent question on dba.stackexchange.com asked “Does T-SQL have a Schema search path?”, similar to PostgreSQL implements the search_pathparameter. This post shows how schemas are implemented in SQL Server. We’ll also see why it’s important to always specify the schema when using SQL Server.

A lot of this behavior goes back to the pre-2005 era. 2005 introduced schemas as logical separators, whereas pre-2005 they were more of a security measure (and dbo was the database owner’s schema). I completely agree that you should specify two-part names in-database. It’s a tiny bit faster (which adds up when you’re doing thousands of transactions per second) and reduces ambiguity.

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