ST_HasNoBand — Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
boolean ST_HasNoBand(raster rast, integer bandnum=1);
Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
Availability: 2.0.0
SELECT rid, ST_HasNoBand(rast) As hb1, ST_HasNoBand(rast,2) as hb2,
ST_HasNoBand(rast,4) as hb4, ST_NumBands(rast) As numbands
FROM dummy_rast;
rid | hb1 | hb2 | hb4 | numbands
-----+-----+-----+-----+----------
1 | t | t | t | 0
2 | f | f | t | 3