1.11 APPROX_FOR_COUNT_DISTINCT

APPROX_FOR_COUNT_DISTINCT automatically replaces COUNT (DISTINCT expr) queries with APPROX_COUNT_DISTINCT queries.

Property	Description
Parameter type	Boolean
Default value	`false`
Modifiable	`ALTER SESSION, ALTER SYSTEM`
Modifiable in a PDB	Yes
Range of values	`true \| false`
Basic	No
Oracle RAC	Different instances can use different values.

Query results for APPROX_COUNT_DISTINCT queries are returned faster than the equivalent COUNT (DISTINCT expr) queries. APPROX_COUNT_DISTINCT queries are useful for situations where a tolerable amount of error is acceptable in order to obtain faster query results than with a COUNT (DISTINCT expr) query.

Note:

This initialization parameter is available starting with Oracle Database 12c Release 2 (12.2.0.1).