oracle计算null值，这更合适

Question

Oracle计数为Null，两者返回的结果相同，但更推荐哪个？还是有更好的方法？

COUNT(DECODE(RESP_CD, NULL, 'X'))

与

NVL(SUM(DECODE(RESP_CD, NULL, 1, 0)), 0)

Answer 1

SELECT SUM(n_count), SUM(x_count)
FROM
     (SELECT CASE WHEN resp_cd IS NULL THEN 1 END n_count,
          CASE WHEN resp_cd = 'x' THEN 1 END x_count
     FROM your_table
     );