addbandarg — A composite type used as input into the ST_AddBand function defining the attributes and initial value of the new band.
A composite type used as input into the ST_AddBand function defining the attributes and initial value of the new band.
index 
                                integer
                            1-based value indicating the position where the new band will be added amongst the raster's bands. If NULL, the new band will be added at the end of the raster's bands.
pixeltype 
                                text
                            Pixel type of the new band. One of defined pixel types as described in ST_BandPixelType.
initialvalue 
                                double precision
                            Initial value that all pixels of new band will be set to.
nodataval 
                                double precision
                            NODATA value of the new band. If NULL, the new band will not have a NODATA value assigned.