STContains (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
SQL database in Microsoft Fabric
Returns 1 if a geometry instance completely contains another geometry instance. Returns 0 if it does not.
Syntax
.STContains ( other_geometry )
Arguments
other_geometry
Is another geometry instance to compare against the instance on which STContains() is invoked.
Return Types
SQL Server return type: bit
CLR return type: SqlBoolean
Remarks
STContains() always returns null if the spatial reference IDs (SRIDs) of the geometry instances do not match.
Examples
The following example uses STContains() to test two geometry instances to see if the first instance contains the second instance.
DECLARE @g geometry;
DECLARE @h geometry;
SET @g = geometry::STGeomFromText('POLYGON((0 0, 2 0, 2 2, 0 2, 0 0))', 0);
SET @h = geometry::STGeomFromText('POINT(1 1)', 0);
SELECT @g.STContains(@h);