Add description for ST_GeometryN, ST_PointN, ST_InteriorRing

docs/dev/ST_GeometryN.md

@@ -2,28 +2,46 @@
 layout: docs
 title: ST_GeometryN
 category: h2spatial/properties
-description: 
+description: Return a element of a <code>GEOMETRYCOLLECTION</code>
 prev_section: ST_ExteriorRing
 next_section: ST_GeometryType
 permalink: /docs/dev/ST_GeometryN/
 ---
 
-### Signatures
+### Signature
 
 {% highlight mysql %}
+GEOMETRY ST_GeometryN(GEOMETRY geom,integer i);
 {% endhighlight %}
 
 ### Description
 
-
+Returns a element number `i` of a `GEOMETRYCOLLECTION`.
 
 {% include sfs-1-2-1.html %}
 
 ### Examples
 
 {% highlight mysql %}
+SELECT ST_GeometryN('MULTIPOLYGON(((0 0, 3 -1, 1.5 2, 0 0)), 
+                     ((1 2, 4 2, 4 6, 1 6, 1 2)))', 1);
+-- Answer: POLYGON((0 0, 3 -1, 1.5 2, 0 0))
+
+SELECT ST_GeometryN('MULTILINESTRING((1 1, 1 6, 2 2, -1 2),
+                     (1 2, 4 2, 4 6))', 2);
+-- Answer: LINESTRING(1 2, 4 2, 4 6)
+
+SELECT ST_GeometryN('MULTIPOINT((0 0), (1 6), (2 2), (1 2))', 2);
+-- Answer: POINT(1 6)
+
+SELECT ST_GeometryN('GEOMETRYCOLLECTION(
+                     MULTIPOINT((4 4), (1 1), (1 0), (0 3)), 
+                     LINESTRING(2 6, 6 2), POINT(4 4), 
+                     POLYGON((1 2, 4 2, 4 6, 1 6, 1 2)))',3);
+-- Answer: POINT(4 4)
 {% endhighlight %}
 
 ##### See also
 
+* [`ST_NumGeometries`](../ST_NumGeometries)
 * <a href="https://github.com/irstv/H2GIS/blob/master/h2spatial/src/main/java/org/h2gis/h2spatial/internal/function/spatial/properties/ST_GeometryN.java" target="_blank">Source code</a>

docs/dev/ST_InteriorRingN.md

@@ -2,28 +2,34 @@
 layout: docs
 title: ST_InteriorRingN
 category: h2spatial/properties
-description: 
+description: Return the interior ring of a <code>POLYGON</code>
 prev_section: ST_GeometryType
 next_section: ST_IsClosed
 permalink: /docs/dev/ST_InteriorRingN/
 ---
 
-### Signatures
+### Signature
 
 {% highlight mysql %}
+LINESTRING ST_InteriorRing(GEOMETRY geom,integer i);
 {% endhighlight %}
 
 ### Description
 
-
+Returns the hole number`i` of a `POLYGON` or Null if parameter is not a `POLYGON`.
 
 {% include sfs-1-2-1.html %}
 
-### Examples
+### Example
 
 {% highlight mysql %}
+SELECT ST_InteriorRingN('POLYGON((0 0, 10 0, 10 6, 0 6, 0 0), 
+                         (1 1, 2 1, 2 5, 1 5, 1 1), 
+                         (8 5, 8 4, 9 4, 9 5, 8 5))',2);
+-- Answer: LINEARRING(8 5, 8 4, 9 4, 9 5, 8 5)
 {% endhighlight %}
 
 ##### See also
 
+* [`ST_ExteriorRing`](../ST_ExteriorRing)
 * <a href="https://github.com/irstv/H2GIS/blob/master/h2spatial/src/main/java/org/h2gis/h2spatial/internal/function/spatial/properties/ST_InteriorRingN.java" target="_blank">Source code</a>

docs/dev/ST_PointN.md

@@ -2,26 +2,29 @@
 layout: docs
 title: ST_PointN
 category: h2spatial/properties
-description: 
+description: Return the <code>POINT</code> i of a <code>LINESTRING</code>
 prev_section: ST_NumPoints
 next_section: ST_PointOnSurface
 permalink: /docs/dev/ST_PointN/
 ---
 
-### Signatures
+### Signature
 
 {% highlight mysql %}
+POINT ST_PointN(Geometry geometry,integer i);
 {% endhighlight %}
 
 ### Description
 
-
+Returns the `POINT` number `i` of a `LINESTRING` or Null if the input parameter is not a `LINESTRING`.
 
 {% include sfs-1-2-1.html %}
 
-### Examples
+### Example
 
 {% highlight mysql %}
+SELECT ST_PointN('LINESTRING(1 1, 1 6, 2 2, -1 2))', 2);
+-- Answer: POINT(1 6)
 {% endhighlight %}
 
 ##### See also