Chapter 4 QUERYING AND MODIFYING DATA 217 REVIEW
Chapter 4 QUERYING AND MODIFYING DATA 217 REVIEW BREAK Data Filtering Filtering of data is the selection of the required information, using supplied criteria, to create a resultset with only the requested data. Filtering minimizes the use of valuable bandwidth, provides for more efficient applications, and in general better suits the end user and business needs. Formatting data is presenting the information so that more value is produced in the finished product. Formatting information can be as simple as placing output in the correct sequence; however, formatting can also mean the use of highly advanced procedures for the analysis and display of data. DATA SUMMARY . Summarize data by using Transact-SQL. Summarizing information to provide results that collect data in a meaningful manner applies functions against the data that can perform calculations, make decisions, and provide answers by performing data analysis on behalf of the user. All functions are either deterministic or nondeterministic. Whether a function is deterministic or nondeterministic is called the determinism of the function. Deterministic functions always return the same result any time they are called with a specific set of input values. Nondeterministic functions may return different results each time they are called with a specific set of input values. For example, the DATEADD built-in function is deterministic because it always returns the same result for any given set of argument values for its three parameters. GETDATE is not deterministic because it is always invoked with the same argument, yet the value it returns changes each time it is executed.
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