STLineFromText (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns a geometry instance from an Open Geospatial Consortium (OGC) Well-Known Text (WKT) representation augmented with any Z (elevation) and M (measure) values carried by the instance.
Syntax
STLineFromText ( 'linestring_tagged_text' , SRID )
Arguments
linestring_tagged_text
Is the WKT representation of the geometryLineString instance you want to return. linestring_tagged_text is an nvarchar(max) expression.
SRID
Is an int expression representing the spatial reference ID (SRID) of the geometryLineString instance you want to return.
Return Types
SQL Server return type: geometry
CLR return type: SqlGeometry
OGC type: LineString
Remarks
This method throws a FormatException if the input isn't well-formatted. Three-dimension and measured geometry WKT notation from the Open Geospatial Consortium (OGC) Simple Features for SQL Specification version 1.2.1 aren't supported. See examples for the supported representation of Z (elevation) and M (measure) values.
Examples
The following examples use STLineFromText() to create a geometry instance.
Example 1: Two-dimension geometry WKT
DECLARE @g geometry;
SET @g = geometry::STLineFromText('LINESTRING (100 100, 200 200)', 0);
SELECT @g.ToString();
Example 2: Three-dimension geometry WKT
DECLARE @g geometry;
SET @g = geometry::STLineFromText('LINESTRING (100 100 100, 200 200 200)', 0);
SELECT @g.ToString();
Example 3: Two-dimension measured geometry WKT
DECLARE @g geometry;
SET @g = geometry::STLineFromText('LINESTRING (100 100 NULL 100, 200 200 NULL 200)', 0);
SELECT @g.ToString();
Example 4: Three-dimension measured geometry WKT
DECLARE @g geometry;
SET @g = geometry::STLineFromText('LINESTRING (100 100 100 100, 200 200 200 200)', 0);
SELECT @g.ToString();