Question

我如何展示＆＃34; 1＆＃34;而不是NULL？

这是我的表格：

|policies|
    |id| |policy|
      1    abc
      2    def

|insurances|
     |id|  |policy_id| |money|
       1         1       1000
       2         1       2000  
       3         2       3000
       4         2       4000 
       5         1       1000

这里是查询：

 select sum(money) as cash from insurances i
 INNER JOIN policies p ON p.id = i.policy_id
 WHERE i.policy_id = 3
 Group by i.policy_id

在这种情况下，当policy_id = 3时，它显示NULL：

 |cash|
   NULL

我想表明：

 |cash|
   1

我也试过，但没有工作：

 select sum(money)+1 as cash from insurances i
 INNER JOIN policies p ON p.id = i.policy_id
 WHERE i.policy_id = 3
 Group by i.policy_id;

Here is the link

Answer 1

SELECT COALESCE(sum(money), 1) as Cash
FROM (
  SELECT policy_id, money
  FROM
    insurances i INNER JOIN policies p
    ON p.id = i.policy_id
  WHERE
    i.policy_id = 1
) s

编辑或者您可以尝试使用这个小技巧：

SELECT COALESCE(MAX(cash), 1) FROM (
  SELECT sum(money) AS cash
  FROM   insurances i
         INNER JOIN policies p ON p.id = i.policy_id
  WHERE i.policy_id = 3
  GROUP BY i.policy_id
) s

如何在总和中显示另一个值而不是NULL？

1 个答案: