TABLE-VALUED FUNCTIONS next previous – 8 5 13

TABLE-VALUED FUNCTIONS next previous – 8 5 13 8 21 13 The next column shows a number in the sequence, and the previous column shows the number that comes before it. The implementation of the function itself is straightforward. It creates an object that has an ISqlReaderand an ISqlRecordinterface. It is shown next. public class CBernoulli { [SqlFunction(DataAccess = DataAccessKind.None, SystemDataAccess = SystemDataAccessKind.None, IsDeterministic = true, IsPrecise = true)] public static ISqlReader Bernoulli (int preStart, int start, int count) { // create object that implements both // ISqlReader and ISqlRecord BData b = new BData(preStart, start, count); ISqlReader dr = b; //return the ISqlReader return dr; } } The BData object is the more difficult part. In order to work properly, it will have to maintain some state that it updates with each call to ISqlReader.Read(). The constructor must pass in the first two values of the sequence and how long the sequence should be. Each call will change the state to the next value in a Bernoulli sequence. SQL Server also has to be able to find the type of each column in the table produced by the TVF. The BData object has to implement the GetSqlMetaData method. This method is passed in an int and must return the SqlDbType of the column through an instance of a SqlMetaData class. There are also numerous other methods, mostly based on SqlTypes that also have to be implemented.

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