---
title: "LineString | Microsoft Docs"
ms.date: "06/13/2017"
ms.prod: "sql-server-2014"
ms.reviewer: ""
ms.technology: 
ms.topic: conceptual
helpviewer_keywords: 
  - "LineString geometry subtype [SQL Server]"
  - "geometry subtypes [SQL Server]"
ms.assetid: e50d0b86-8b31-4285-be71-ad05c7712cbd
author: MladjoA
ms.author: mlandzic
manager: craigg
---
# LineString
  A `LineString` is a one-dimensional object representing a sequence of points and the line segments connecting them.

## LineString Instances
 The illustration below shows examples of `LineString` instances.

 ![Examples of geometry LineString instances](../../database-engine/media/linestring.gif "Examples of geometry LineString instances")

 As shown in the illustration:

-   Figure 1 is a simple, nonclosed `LineString` instance.

-   Figure 2 is a nonsimple, nonclosed `LineString` instance.

-   Figure 3 is a closed, simple `LineString` instance, and therefore is a ring.

-   Figure 4 is a closed, nonsimple `LineString` instance, and therefore is not a ring.

### Accepted Instances
 Accepted `LineString` instances can be input into a geometry variable, but they may not be valid `LineString` instances. The following criteria must be met for a `LineString` instance to be accepted. The instance must be formed of at least two points or it must be empty. The following LineString instances are accepted.

```
DECLARE @g1 geometry = 'LINESTRING EMPTY';
DECLARE @g2 geometry = 'LINESTRING(1 1,2 3,4 8, -6 3)';
DECLARE @g3 geometry = 'LINESTRING(1 1, 1 1)';
```

 `@g3` shows that a `LineString` instance can be accepted, but not valid.

 The following `LineString` instance is not accepted. It will throw a `System.FormatException`.

```
DECLARE @g geometry = 'LINESTRING(1 1)';
```

### Valid Instances
 For a `LineString` instance to be valid it must meet the following criteria.

1.  The `LineString` instance must be accepted.

2.  If a `LineString` instance is not empty then it must contain at least two distinct points.

3.  The `LineString` instance cannot overlap itself over an interval of two or more consecutive points.

 The following `LineString` instances are valid.

```
DECLARE @g1 geometry= 'LINESTRING EMPTY';
DECLARE @g2 geometry= 'LINESTRING(1 1, 3 3)';
DECLARE @g3 geometry= 'LINESTRING(1 1, 3 3, 2 4, 2 0)';
DECLARE @g4 geometry= 'LINESTRING(1 1, 3 3, 2 4, 2 0, 1 1)';
SELECT @g1.STIsValid(), @g2.STIsValid(), @g3.STIsValid(), @g4.STIsValid();

```

 The following `LineString` instances are not valid.

```
DECLARE @g1 geometry = 'LINESTRING(1 4, 3 4, 2 4, 2 0)';
DECLARE @g2 geometry = 'LINESTRING(1 1, 1 1)';
SELECT @g1.STIsValid(), @g2.STIsValid();
```

> [!WARNING]
>  The detection of `LineString` overlaps is based on floating-point calculations, which are not exact.

## Examples
 The following example shows how to create a `geometry``LineString` instance with three points and an SRID of 0:

```
DECLARE @g geometry;
SET @g = geometry::STGeomFromText('LINESTRING(1 1, 2 4, 3 9)', 0);
```

 Each point in the `LineString` instance may contain Z (elevation) and M (measure) values. This example adds M values to the `LineString` instance created in the example above. M and Z can be null values.

```
DECLARE @g geometry;
SET @g = geometry::STGeomFromText('LINESTRING(1 1 NULL 0, 2 4 NULL 12.3, 3 9 NULL 24.5)', 0);
```

 The following example shows how to create a `geometry LineString` instance with two points that are the same. A call to `IsValid` indicates that the `LineString` instance is not valid and a call to `MakeValid` will convert the `LineString` instance into a `Point`.

```sql
DECLARE @g geometry
SET @g = geometry::STGeomFromText('LINESTRING(1 3, 1 3)',0);
IF @g.STIsValid() = 1
  BEGIN
     SELECT @g.ToString() + ' is a valid LineString.';  
  END
ELSE
  BEGIN
     SELECT @g.ToString() + ' is not a valid LineString.';
     SET @g = @g.MakeValid();
     SELECT @g.ToString() + ' is a valid Point.';  
  END

```

 The above code snippet will return the following:

```
LINESTRING(1 3, 1 3) is not a valid LineString
POINT(1 3) is a valid Point.
```

## See Also
 [STLength (geometry Data Type)](/sql/t-sql/spatial-geometry/stlength-geometry-data-type) 
 [STStartPoint (geometry Data Type)](/sql/t-sql/spatial-geometry/ststartpoint-geometry-data-type) 
 [STEndpoint (geometry Data Type)](/sql/t-sql/spatial-geometry/stendpoint-geometry-data-type) 
 [STPointN (geometry Data Type)](/sql/t-sql/spatial-geometry/stpointn-geometry-data-type) 
 [STNumPoints (geometry Data Type)](/sql/t-sql/spatial-geometry/stnumpoints-geometry-data-type) 
 [STIsRing (geometry Data Type)](/sql/t-sql/spatial-geometry/stisring-geometry-data-type) 
 [STIsClosed (geometry Data Type)](/sql/t-sql/spatial-geometry/stisclosed-geometry-data-type) 
 [STPointOnSurface (geometry Data Type)](/sql/t-sql/spatial-geometry/stpointonsurface-geometry-data-type) 
 [Spatial Data (SQL Server)](../spatial/spatial-data-sql-server.md)