> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kinetica.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Filtered Views

A *filtered view* is a queryable filter of a [table](/content/concepts/tables#table) or
another *view*. A *filtered view* can be created by filtering an existing
*table* or *view* using the `/filter` endpoint.

<Info>
  For SQL views, see [CREATE VIEW](/content/sql/ddl#sql-create-view).
</Info>

Given the need to minimize memory usage,
*filtered views* are given a default [time-to-live](/content/concepts/ttl), after
which they will expire and be removed from memory.  Each access of the
*filtered view* causes the remaining *time-to-live* to be reset.  Thus, a
*filtered view* accessed more frequently than its *time-to-live* will
effectively remain in memory indefinitely.

A *filtered view* name must adhere to the standard
[naming criteria](/content/concepts/tables#table-naming-criteria).  Each *filtered view*
exists within a [schema](/content/concepts/schemas) and follows the standard
[name resolution rules](/content/concepts/tables#table-name-resolution) for *tables*.

## Creating a Filtered View

To create a *filtered view*, the [/filter](/content/api/rest/filter_rest) endpoint
requires three parameters:

1. the name of the data set to create the *filtered view* from
2. the name of the *filtered view* to create
3. an expression used to filter the source data set

### Examples

In *Python*, given the `nyctaxi` demo table, a *filtered view* can be created
for all taxi rides from the `YCAB` vendor via:

```python theme={null}
kinetica.filter(
    table_name = "demo.nyctaxi",
    view_name = "example.nyctaxi_ycab",
    expression = "vendor_id = 'YCAB'"
)
```

The resulting *filtered view* can then be further filtered for expensive
single-passenger rides:

```python theme={null}
kinetica.filter(
    table_name = "example.nyctaxi_ycab",
    view_name = "example.nyctaxi_ycab_single_expensive",
    expression = "passenger_count = 1 and total_amount > 150"
)
```

## Limitations and Cautions

* When a record contained in a *filtered view* is modified by an update of the
  underlying data set, the record is removed from the *filtered view* regardless
  of whether the update impacted the record's qualifications for membership in
  the *filtered view*.
* When a *table* or *view* is dropped, all of the *filtered views* created from
  it are also automatically cleared.
* Records accessible through a *filtered view* cannot be added, edited, or
  deleted through that same *view*.
* A *filtered view* is transient, by default, and will expire after the default
  [TTL](/content/concepts/ttl) setting.
* A *filtered view* is not persisted, and will not survive a database restart.

### Memory Implications

A *filtered view* has a relatively lower memory footprint compared to a
[join](/content/concepts/joins) *view* or a
[memory-only table](/content/concepts/tables_memory_only), such as a
[projection](/content/concepts/projections) or [union](/content/concepts/unions). Read
more about *memory-only tables* and their relative memory implications on
[Memory-Only Tables](/content/concepts/tables_memory_only).