mysql case when多条件同时满足的多个and组合嵌套的情况，判断空is null --- 系列一

Bertha 。 2021-09-16 01:24 1729阅读 0赞

## [mysql case when多条件同时满足的多个and组合嵌套的情况，判断空is null --- 系列][mysql case when_and_is null ---]二 ##

## [https://blog.csdn.net/qb170217/article/details/81534399][mysql case when_and_is null ---] ##

## case when不支持下面2这种写法(我已经测试过了，大侠如有好办法，麻烦分享)： ##

情况1：未加括号

select 
    wf.fid id,
    CASE 
    WHEN wf.Fstep = 1 AND wf.Fstatus = 'Reject' and wf.Foper_reason IS NULL THEN '未填写驳回理由'
    WHEN wf.Fstep = 1 AND wf.Fstatus = 'Reject' and wf.Foper_reason IS NOT NULL THEN wf.Foper_reason
    END reason,
    wf.Fcreate_time time
    from t_work_flow wf 
    order by time desc;

情况2：加括号

select 
    wf.fid id,
    CASE 
    WHEN (wf.Fstep = 1 AND wf.Fstatus = 'Reject') and wf.Foper_reason IS NULL THEN '未填写驳回理由'
    WHEN (wf.Fstep = 1 AND wf.Fstatus = 'Reject') and wf.Foper_reason IS NOT NULL THEN wf.Foper_reason
    END reason,
    wf.Fcreate_time time
    from t_work_flow wf 
    order by time desc;

### 更改后就可以了 ###

SELECT id, 
    CASE when reason is null THEN '未填写驳回理由' 
    ELSE reason 
    END reason,
    time from 
    (
    select 
    wf.fid id,
    CASE 
    WHEN wf.Fstep = 1 AND wf.Fstatus = 'Reject' and wf.Foper_reason IS NULL THEN '未填写驳回理由'
    WHEN wf.Fstep = 1 AND wf.Fstatus = 'Reject' and wf.Foper_reason IS NOT NULL THEN wf.Foper_reason
    END reason,
    wf.Fcreate_time time
    from t_work_flow wf
    ) result
    order by time desc;

[mysql case when_and_is null ---]: https://blog.csdn.net/qb170217/article/details/81534399