ST_Z
Name
ST_Z — Returns the Z coordinate of a Point.
Synopsis
    
     float
     
      ST_Z
     
     (
    
    geometry
    
     a_point
    
    
     )
    
    ;
   
Description
Return the Z coordinate of the point, or NULL if not available. Input must be a point.
       
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| 
       To get the minimum and maximum Z value of geometry coordinates use the functions ST_ZMin and ST_ZMax .  | 
    
   
    
   
   This method implements the SQL/MM specification.
  
   
    
   
   This function supports 3d and will not drop the z-index.