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%