Default values for search arguments

When statistics are not available for a search argument or when the value of a search argument is not known at optimization, the optimizer uses default values. These values are shown in Table 2-2.

**Table 2-2: Density approximations for unknown search arguments**
Operation Type	Operator	Density Approximation
Equality	=	Total density, if statistics are available for the column, or 10%
Open-ended range	<, <=, >, or >=	33%
Closed range	between	25%