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

# MULTILINESTRING

export const InternalLink = ({version, path = "", children, ...props}) => {
  let detectedVersion = version || "stable";
  if (typeof window !== 'undefined' && !version) {
    const match = window.location.pathname.match(/\/docs\/([^/]+)/);
    if (match) {
      detectedVersion = match[1];
    }
  }
  const normalizedPath = path.startsWith("/") ? path.slice(1) : path;
  return <a href={`/docs/${detectedVersion}/${normalizedPath}`} {...props}>
      {children}
    </a>;
};

A `MULTILINESTRING` is a collection of <InternalLink path="linestring">LineStrings</InternalLink>.  MultiLineStrings are useful for gathering a group of LineStrings into one geometry. For example, you may want to gather the LineStrings denoting all of the roads in a particular municipality.

You can also store a \`\` with the following additional dimensions:

* A third dimension coordinate `Z` (`Z`).
* A measure coordinate `M` (`M`).
* Both a third dimension and a measure coordinate (`ZM`).

The `Z` and `M` dimensions can be accessed or modified using a number of <InternalLink path="functions-and-operators">built-in functions</InternalLink>, including:

* `ST_Z`
* `ST_M`
* `ST_Affine`
* `ST_Zmflag`
* `ST_MakePoint`
* `ST_MakePointM`
* `ST_Force3D`
* `ST_Force3DZ`
* `ST_Force3DM`
* `ST_Force4D`
* `ST_Snap`
* `ST_SnapToGrid`
* `ST_RotateZ`
* `ST_AddMeasure`

Note that CockroachDB's <InternalLink path="spatial-indexes">spatial indexing</InternalLink> is still based on the 2D coordinate system.  This means that:

* The Z/M dimension is not index accelerated when using spatial predicates.
* Some spatial functions ignore the Z/M dimension, with transformations discarding the Z/M value.

## Examples

### Well known text

A MultiLineString can be created from SQL by calling the `st_geomfromtext` function on a MultiLineString definition expressed in the <InternalLink path="architecture/glossary#wkt">Well Known Text (WKT)</InternalLink> format.

```sql theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}}
SELECT ST_GeomFromText('MULTILINESTRING((0 0, 1440 900), (800 600, 200 400))');
```

```
                                                                                     st_geomfromtext
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  0105000000020000000102000000020000000000000000000000000000000000000000000000008096400000000000208C4001020000000200000000000000000089400000000000C0824000000000000069400000000000007940
(1 row)
```

### SQL

A MultiLineString can be created from SQL by calling an aggregate function such as `ST_Collect` or <InternalLink path="st_union">`ST_Union`</InternalLink> on a column that contains <InternalLink path="linestring">LineString</InternalLink> geometries.  In the example below, we will build a MultiLineString from several LineStrings.

1. Insert the LineStrings:

   ```sql theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}}
   CREATE TABLE tmp_linestrings (id INT8 default unique_rowid(), geom GEOMETRY);

   INSERT INTO tmp_linestrings (geom)
   VALUES
   (st_geomfromtext('SRID=4326;LINESTRING(-88.243385 40.116421, -87.906471 43.038902, -95.992775 36.153980)')),
   (st_geomfromtext('SRID=4326;LINESTRING(-75.704722 36.076944, -95.992775 36.153980, -87.906471 43.038902)')),
   (st_geomfromtext('SRID=4326;LINESTRING(-76.8261 42.1727,  -75.6608 41.4102,-73.5422 41.052, -73.929 41.707,  -76.8261 42.1727)'));
   ```

2. Build a MultiLineString from the individual <InternalLink path="linestring">LineStrings</InternalLink> using `ST_Collect`, and check the output with `ST_GeometryType` to verify that it is indeed a MultiLineString:

   ```sql theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}}
   SELECT ST_GeometryType(st_collect(geom)) AS output FROM tmp_linestrings;
   ```

   ```
           output
   ----------------------
     ST_MultiLineString
   (1 row)
   ```

3. Drop the temporary table:

   ```sql theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}}
   DROP TABLE tmp_linestrings;
   ```

## See also

* <InternalLink path="spatial-data-overview#spatial-objects">Spatial objects</InternalLink>
* <InternalLink path="point">POINT</InternalLink>
* <InternalLink path="linestring">LINESTRING</InternalLink>
* <InternalLink path="polygon">POLYGON</InternalLink>
* <InternalLink path="multipoint">MULTIPOINT</InternalLink>
* <InternalLink path="multipolygon">MULTIPOLYGON</InternalLink>
* <InternalLink path="geometrycollection">GEOMETRYCOLLECTION</InternalLink>