減法不SUM

Question

正常工作之後我的查詢：

SELECT SUM(t*q) as first, 
SUM(s*q) AS second, 
SUM(t*q)-SUM(s*q) AS firstminussecond 
FROM my_table 

結果是：

first = 9010.56 
second = 8664 
firstminussecond = 346.5599999999995 (this should be 346.56!) 

爲什麼firstminussecond是不正確的？如何解決這個問題？

Answer 1

我發現在我看來，正確的解決方案，我改變了列t和s數據類型DECIMAL(10,2)和q到INT(11)。現在firstminussecond是正確的。

Answer 2

試試這個，

SELECT 
      ROUND(SUM(t*q),2) as first, 
      ROUND(SUM(s*q),2) AS second, 
      (
      ROUND(SUM(t*q),2)- 
      ROUND(SUM(s*q),2) 
      ) AS firstminussecond 
    FROM my_table 

OR

SELECT 
      ROUND(SUM(t*q),2) as first, 
      ROUND(SUM(s*q),2) AS second, 
      ROUND(
        (ROUND(SUM(t*q),2)- 
        ROUND(SUM(s*q),2)) 
       ,2) AS firstminussecond 
    FROM my_table 

Answer 3

您可以通過這個嘗試：

SELECT SUM(t*q) as first, 
SUM(s*q) AS second, 
FORMAT(SUM(t*q)-SUM(s*q),2) AS firstminussecond 
FROM my_table 

Answer 4

SELECT SUM(t*q) as first, 
SUM(s*q) AS second, 
cast(SUM(t*q)-SUM(s*q) as decimal(5,2)) AS firstminussecond 
FROM my_table 

Answer 5

您需要使用ROUND功能。

SELECT SUM(t*q) AS first, 
SUM(s*q) AS second, 
ROUND(SUM(t*q)-SUM(s*q), 2) AS firstminussecond 
FROM my_table