SQL 仅更新其值尚未更新的值答案

【问题标题】：SQL update only values whose value is not already updatedSQL 仅更新其值尚未更新的值
【发布时间】：2016-08-04 06:57:17
【问题描述】：

我有一个查询，它会更新表中的所有票证。我希望它只更新其值需要更新的票，而不是更新所有行。例如如果slabreachdays 已经是10，那么新值也是10，它不应该更新。这是我的更新查询。

update ticket 
set TICKET.slabreachdays =
FLOOR(((DAYS(TICKET.creationdate) - DAYS(current timestamp)+10) 
* 86400 + (MIDNIGHT_SECONDS(TICKET.creationdate) -
MIDNIGHT_SECONDS(current timestamp)))/86400.0)
where TICKET.VENDOR like 'ABC' 
and TICKET.STATUS NOT IN('CANCELLED','CLOSED')

这是我的选择查询，它只选择需要更新的票证。这是我需要转换为更新查询的查询

select * from (
    select ticketid,slabreachdays,
    FLOOR(((DAYS(TICKET.creationdate) - DAYS(current timestamp)+10) * 86400 + (MIDNIGHT_SECONDS(TICKET.creationdate) - MIDNIGHT_SECONDS(current timestamp)))/86400.0)
    as newValue
    from ticket
    where TICKET.MLOUTSOURCEVENDOR like 'ABC' and TICKET.STATUS NOT IN('CANCELLED','CLOSED'))
where SLABREACHDAYS != newValue

【问题讨论】：

标签： sql database db2

【解决方案1】：

试试看

Where .... 和slabeachdays aller 计算表达式

【讨论】：

【解决方案2】：

试试这个

update ticket 
set TICKET.slabreachdays =
FLOOR(((DAYS(TICKET.creationdate) - DAYS(current timestamp)+10) 
* 86400 + (MIDNIGHT_SECONDS(TICKET.creationdate) -
MIDNIGHT_SECONDS(current timestamp)))/86400.0)
where TICKET.VENDOR like 'ABC' 
and TICKET.STATUS NOT IN('CANCELLED','CLOSED') and
TICKET.slabreachdays <>
(FLOOR(((DAYS(TICKET.creationdate) - DAYS(current timestamp)+10) 
* 86400 + (MIDNIGHT_SECONDS(TICKET.creationdate) -
MIDNIGHT_SECONDS(current timestamp)))/86400.0))

【讨论】：