90 Part I EXAM PREPARATION a globally unique
90 Part I EXAM PREPARATION a globally unique identifier or GUID. The GUID takes on the string format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, in which each x is a hexadecimal digit. A GUID is long and obscure, but has the advantage of being guaranteed to be unique throughout the world. The sql_variant is a generic data type that stores values of various SQL Server-supported data types, except text, ntext, image, timestamp, and sql_variant. It may be used in column definitions as well as in parameters, variables, and return values of user-defined functions. A sql_variant can have a maximum length of 8,016 bytes. The table data type is new to SQL Server in the 2000 release. It can be used to temporarily store a resultset for later use. The table data type is not used for defining column types within a structure; rather it is used in functions, stored procedures, and batches. The cursor data type is another data type that is used only in functions, stored procedures, and batches. Its primary purpose is to allow the storage of a pointer to a resultset. Attributes of a T-SQL server cursor, such as its scrolling behavior and the query used to build the resultset on which the cursor operates, are set up using a DECLARE CURSOR operation within the procedure. User-Defined Data Types User-defined data types are stored as database objects and are based on any of the system data types. User-defined data types can be used when several tables must store the same type of data in a column and you must ensure that these columns have exactly the same data type, length, and nullability. Using these data types can help you create tables more quickly and can also help you control the data in a predictable manner. Often a user-defined data type is created in the model database; it will then exist in all new user-defined databases created. Data Types in a Logical Model Data definition is a step that follows the ER modeling as the database system nears the stage where it can be designed for the actual physical implementation. If present at all, the data definition in the logical model is more a general characterization of the data as
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