mysql - 是否有可能将其显示为 0 而不是 NULL？

Question

代码：

SELECT 
  count(*) as count, 
  sum(Status = 'test1') as count_test1, 
  sum(Status = 'test2') as count_test2
FROM Table
WHERE Type = 'test'

结果我看到：

count   count_test1   count_test2
  0       NULL           NULL

请告诉我，是否有可能使显示 0 而不是 NULL？

PS：结果是：

count   count_test1   count_test2
  0       0               0

Answer 1

您可以使用COALESCE

COALESCE(sum(Status = 'test1'), 0)

或者IFNULL

IFNULL(sum(Status = 'test1'), 0)

Answer 2

SELECT 
  count(*) as count, 
      IFNULL(sum(Status = 'test1'), 0) as count_test1, 
      IFNULL(sum(Status = 'test2'), 0) as count_test2
FROM Table
WHERE Type = 'test'

Answer 3

您可以使用COALESCE接受数组并返回第一个元素不为空的函数

SELECT 
  count(*) as count, 
  COALESCE(sum(Status = 'test1'), 0) as count_test1, 
  COALESCE(sum(Status = 'test2'), 0) as count_test2
FROM Table
WHERE Type = 'test'