<h3>combine function</h3>
Returns the combination of geometry a and geometry b.

<h4>Syntax</h4>
<pre>combine( geometry a , geometry b)</pre>

<h4>Arguments</h4>
geometry &rarr; geometry
geometry &rarr; geometry

<h4>Example</h4>
<pre> geomToWKT( combine( geomFromWKT( 'LINESTRING(3 3 , 4 4 , 5 5 )' ) , geomFromWKT( 'LINESTRING(3 3 , 4 4,  2 1 )' ))  )    &rarr; returns MULTILINESTRING((4 4, 2 1), (3 3, 4 4), (4 4, 5 5)) </pre>
<pre> geomToWKT( combine( geomFromWKT( 'LINESTRING(3 3 , 4 4  )' ) , geomFromWKT( 'LINESTRING(3 3 , 6 6,  2 1 )' ))  )  &rarr; returns LINESTRING(3 3, 4 4, 6 6, 2 1) </pre>
