Exam 70-764 topic 1 question 166 discussion

DRAG DROP -
You plan to deploy SQL Server 2012. You must create two tables named Table 1 and Table 2 that will have the following specifications:
✑ Table1 will contain a date column named Column1 that will contain a null value approximately 80 percent of the time.
✑ Table2 will contain a column named Column2 that is the product of two other columns in Table2.
Both Table1 and Table2 will contain more than 1 million rows.
You need to recommend which options must be defined for the columns. The solution must minimize the storage requirements for the tables.
Which options should you recommend? To answer, drag the appropriate options to the correct column in the answer area.
Select and Place:

Suggested Answer:
- Sparse columns are ordinary columns that have an optimized storage for null values. Sparse columns reduce the space requirements for null values at the cost of more overhead to retrieve nonnull values. Consider using sparse columns when the space saved is at least 20 percent to 40 percent.
- A Persisted column would be faster to retrieve.
- A computed column is computed from an expression that can use other columns in the same table. The expression can be a noncomputed column name, constant, function, and any combination of these connected by one or more operators. Unless otherwise specified, computed columns are virtual columns that are not physically stored in the table. Their values are recalculated every time they are referenced in a query. The Database Engine uses the PERSISTED keyword in the CREATE TABLE and ALTER TABLE statements to physically store computed columns in the table. Their values are updated when any columns that are part of their calculation change.
References:
http://msdn.microsoft.com/en-us/library/cc280604.aspx
http://msdn.microsoft.com/en-us/library/ms186241.aspx