Oracle decode()函数应用

在项目第一次遇到decode()函数，简单写一下用法。

 select count(*),sum(decode(fz.station_class_f, '租用机房', '', '')),
        sum(decode(fz.station_class_f, '自建彩钢板机房', '', '')),
        sum(decode(fz.station_class_f, '自建砖混机房', '', '')),
        sum(decode(fz.station_class_f, '一体化机柜', '', '')),
        sum(decode(fz.station_class_f, 'RRU拉远', '', '')),
        sum(decode(fz.station_class_f, '其他机房', '', '')),
        sum(decode(fz.station_class_f, '无机房', '', ''))
        from wg_jzmb jz, wg_jzfz fz
  where jz.station_code = fz.station_code
    and jz.STATION_STAT in ('启用', '暂停支付')

decode(条件1，值1，值2，值3)  如上格式所示

decode(fz.station_class_f, '自建彩钢板机房', '1', '0')

fz.station_class_f字段等于 "自建彩钢板机房" 字符串时，取到值"1"，若不等于取到值"0"
再通过sum()函数完成对该数据的累加计算。