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.
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