In SQL Server 2008, you can perform insert, update, or delete operations in a single statement using the MERGE statement.
The MERGE statement allows you to join a data source with a target table or view, and then perform multiple actions against the target based on the results of that join.
For example, you can use the MERGE statement to perform the following operations: It is important to understand how the source and target data are merged into a single input stream and how additional search criteria can be used to correctly filter out unneeded rows.
Otherwise,you might specify the additional search criteria in a way that produces incorrect results.
The system checks for the violation of the constraints on actions that may cause a violation, and aborts the action accordingly.
Information on SQL constraints can be found in the textbook.
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This schema is read-only and contains some views and other schema objects. The catalog name has no relation to the file name of the database. Schema objects are database objects that contain data or govern or perform operations on data.
The views contain lists of all the database objects that exist within the catalog, plus all authorizations. A name is an identifier and is unique within its name-space. Each database has also an internal "unique" name which is automatically generated when the database is created. By definition, each schema object belongs to a specific schema.
A catalog contains schemas, and schemas contain the objects that contain data or govern the data.
Each catalog contains a special schema called INFORMATION_SCHEMA.