Mysql 如何使用SQL查询在表中的两个字段之间执行减法

我想使用SQL查询显示从两个不同列到第三列的两个值的减法

这是表结构：

------------------------------------
id | subject | Time1 | Time2| Time3
------------------------------------
1  | String1 | 50    |  78  | 
2  | String2 | 60    |  99  |  
3  |         |       |      |

如果Time1和Time2都有数据并存储在Time3中，我想从Time1中减去Time2

输出应该像

------------------------------------
id | subject | Time1 | Time2| Time3
------------------------------------
1  | String1 | 50    |  78  |  28
2  | String2 | 60    |  99  |  39
3  |         |       |      |

---

谢谢

假设

Time1

和

Time2

是数字列，您可以使用简单的减法：

SELECT
    id
    ,subject
    ,Time1
    ,Time2
    ,Time2-Time1 as Time3
FROM tbl

select id, subject, Time1, Time3, Time2 - Time1 as Time3 from myTable

---

假设

Time1

和

Time2

是数字列，您可以使用简单的减法：

select id, subject, Time1, Time3, Time2 - Time1 as Time3 from myTable

试试这个

select id, subject, Time1, Time2, Time2-Time1 as Time3  from mytable

试试这个

select id, subject, Time1, Time2, Time2-Time1 as Time3  from mytable

---

这将检查

Time1

和

Time2

中是否存在数据：如果有足够的数据，

Time3=Time2-Time1

；否则为

null

select id, subject, Time1, Time2, 
   ifnull(Time1, null, ifnull(Time2, null, Time2 - Time1)) as Time3 
from myTable

---

这将检查

Time1

和

Time2

中是否存在数据：如果有足够的数据，

Time3=Time2-Time1

；否则为

null

select id, subject, Time1, Time2, 
   ifnull(Time1, null, ifnull(Time2, null, Time2 - Time1)) as Time3 
from myTable

试试这个

SELECT *, `Time2`-`Time1` AS `Time3` FROM `tablename`

SELECT id, subject, Time1, Time2, CONCAT(Time2 - Time1) AS Time3 FROM tabel

试试这个

SELECT *, `Time2`-`Time1` AS `Time3` FROM `tablename`

SELECT id, subject, Time1, Time2, CONCAT(Time2 - Time1) AS Time3 FROM tabel

---

如果Time1和Time2是datetime字段，那么您应该在MySQL中使用

TIMEDIFF

函数来正确格式化Time3字段

SELECT id, subject, Time1, Time2, TIMEDIFF(Time1, Time2) as Time3 
  FROM tbl

---

如果Time1和Time2是datetime字段，那么您应该使用MySQL中的

TIMEDIFF

函数来正确设置Time3字段的格式

SELECT id, subject, Time1, Time2, TIMEDIFF(Time1, Time2) as Time3 
  FROM tbl

试试这个

SELECT *, `Time2`-`Time1` AS `Time3` FROM `tablename`

SELECT id, subject, Time1, Time2, CONCAT(Time2 - Time1) AS Time3 FROM tabel

试试这个

SELECT *, `Time2`-`Time1` AS `Time3` FROM `tablename`

SELECT id, subject, Time1, Time2, CONCAT(Time2 - Time1) AS Time3 FROM tabel

---

@克丽丝：那么我的助理应该工作了。试试看。如果我的回答有帮助，请接受正确答案。当然，我还没有检查解决方案；将检查并更新。如果Time1/2字段中的任何一个为空，我不想进行计算。@kris那么我的asnwer应该可以工作。试试看。如果我的回答有帮助，请接受正确答案。当然，我还没有检查解决方案；将检查并更新。如果任何Time1/2字段为空，我不想进行计算。请编辑以格式化代码，好吗？突出显示所有代码并按Ctrl+K是否可以编辑以格式化代码？高亮显示所有代码并按Ctrl+K