c# - 更新满足 datediff 约束的所有行的 int 列？

Question

我有一个每 30 秒运行一次的函数，我想更新所有行中的列，其中 current time - table.lastStoredTime > 5 minutes。

lastStoredTime 是一个日期时间列，我似乎无法正常工作。

尝试(不更新行)

SELECT  
    DATEDIFF(MINUTE, t.lastStoredTime, CURRENT_TIMESTAMP) AS Mtime 
FROM Transaction_tbl t 
WHERE 
    AND DATEDIFF(MINUTE,t.lastStoredTime, CURRENT_TIMESTAMP) > 5

Answer 1

测试设置:

create table Transaction_tbl (id int identity(1,1) not null, lastStoredTime datetime2(7), intcol int)
insert into Transaction_tbl 
          select dateadd(minute,-7,sysdatetime()), 0
union all select dateadd(minute,-6,sysdatetime()), 0
union all select dateadd(minute,-5,sysdatetime()), 0
union all select dateadd(minute,-4,sysdatetime()), 0
union all select dateadd(minute,-3,sysdatetime()), 0

查询:

/* select */
select *,
  datediff(minute, t.lastStoredTime, sysdatetime()) as Mtime 
from Transaction_tbl t 
where t.lastStoredTime < dateadd(minute,-5,sysdatetime())

/* as an update */
update t
  set intcol = intcol+1
output inserted.*
from Transaction_tbl t 
where t.lastStoredTime < dateadd(minute,-5,sysdatetime())

rextester 演示:http://rextester.com/TXYXT83237

选择输出:

+----+---------------------+--------+-------+
| id |   lastStoredTime    | intcol | Mtime |
+----+---------------------+--------+-------+
|  1 | 2017-08-22 19:31:52 |      0 |     7 |
|  2 | 2017-08-22 19:32:52 |      0 |     6 |
|  3 | 2017-08-22 19:33:52 |      0 |     5 |
+----+---------------------+--------+-------+

更新输出:

+----+---------------------+--------+
| id |   lastStoredTime    | intcol |
+----+---------------------+--------+
|  1 | 2017-08-22 19:31:52 |      1 |
|  2 | 2017-08-22 19:32:52 |      1 |
|  3 | 2017-08-22 19:33:52 |      1 |
+----+---------------------+--------+

---

使用 case 表达式更新:

update t
  set intcol = case when t.lastStoredTime < dateadd(minute,-5,sysdatetime()) 
      then intcol+1
      else intcol-1
      end
output inserted.*
from Transaction_tbl t 

输出:

+----+---------------------+--------+
| id |   lastStoredTime    | intcol |
+----+---------------------+--------+
|  1 | 2017-08-22 19:47:14 |      2 |
|  2 | 2017-08-22 19:48:14 |      2 |
|  3 | 2017-08-22 19:49:14 |     -1 |
|  4 | 2017-08-22 19:50:14 |     -1 |
|  5 | 2017-08-22 19:51:14 |     -1 |
+----+---------------------+--------+