Question

我尝试用SQL计算。计算结果显示在图表中。如果sql查询的结果为空，则图表停止工作：

这是我正在使用的SQL查询：

SELECT SUM(total) as total
FROM table
WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31'

如果表中有数据，则没有问题。当没有数据时，图表停止工作。

所以如果总数为空，我想显示'0'。如果它是空的，我需要在SQL查询中更改为显示“0”？

Answer 1

如果表为空，则使用COALESCE返回0而不是NULL：

SELECT COALESCE(SUM(total),0) as total
FROM table
WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31'

Answer 2

你试过了吗？

SELECT ISNULL(SUM(total), 0) as total
FROM table
WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31'

Answer 3

此查询将始终返回一行，如果没有匹配的行，则默认为零：

SELECT COALESCE((
  SELECT 
    SUM(total)
  FROM table
  WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31'
),0) AS total

Answer 4

你可以试试这个：

if not exists (SELECT total FROM table WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31')
begin 
    select 0 as total
end
else
begin
    SELECT SUM(total) as total
    FROM table
    WHERE user_id = 1 AND date BETWEEN '2016-06-01' AND '2016-06-31'
end

如果结果为空，则显示“0”

4 个答案: