# ST_EnvIntersects function

The ST_EnvIntersects function takes two geometries of the same spatial reference system as input parameters and returns 1 if the envelopes of the two geometries intersect. Otherwise, 0 (zero) is returned.

If the second geometry is not represented in the same spatial reference system as the first geometry, the routine will return -1. The geometries must be converted into the same spatial reference system to determine the relation, see ST_Transform.

If any of the specified geometries is null or is empty, then the null value is returned.

## Syntax

## Parameter

- geometry1
- A value of type ST_Geometry or one of its subtypes that represents
the geometry whose envelope is to be tested for intersection with
the envelope of
*geometry2*. - geometry2
- A value of type ST_Geometry or one of its subtypes that represents
the geometry whose envelope is to be tested for intersection with
the envelope of
*geometry1*.

## Return type

INTEGER

## Example

This example creates two parallel
linestrings and checks them for intersection. The linestrings themselves
do not intersect, but the envelopes for them do.

```
CREATE TABLE sample_geoms (id INTEGER, geometry ST_Geometry)
INSERT INTO sample_geoms VALUES
(1, ST_Geometry('linestring (10 10, 50 50)',0))
INSERT INTO sample_geoms VALUES
(2, ST_Geometry('linestring (10 20, 50 60)',0))
SELECT a.id, b.id, ST_Intersects(a.geometry, b.geometry) Intersects,
ST_EnvIntersects(a.geometry, b.geometry) Envelope_Intersects
FROM sample_geoms a , sample_geoms b
WHERE a.id = 1 and b.id=2
```

Results:

```
ID ID INTERSECTS ENVELOPE_INTERSECTS
----------- ----------- ----------- -------------------
1 2 0 1
```