Name
ST_BandNoDataValue — 返回给定区段中表示无数据的值。如果没有频带数，则假定为1。
Synopsis
double precision ST_BandNoDataValue(raster rast, integer bandnum=1);
示例
SELECT ST_BandNoDataValue(rast,1) As bnval1,
ST_BandNoDataValue(rast,2) As bnval2, ST_BandNoDataValue(rast,3) As bnval3
FROM dummy_rast
WHERE rid = 2;
bnval1 | bnval2 | bnval3
--------+--------+--------
0 | 0 | 0