查询以获取条件的最小日期

Question

   create table t(dt1 date,dt2 date,dt3 date,dt4 date)

    insert into t values('1970-01-01','2008-10-10',NULL,NULL),
(NULL,'2008-10-10','2017-10-12',NULL),('1970-01-01','2008-10-10',NULL,'2018-10-09')

我已对此查询进行了编码

select *, (select min(dates) 
           from (values (dt1), (dt2), (dt3), (dt4))a(dates)
           where a.dates > '1970-01-01') as DDt
from t;

但它没有处理黑斑羚并且在下面给出错误 -

^ encountered Exception syntax error

Answer 1

试试这个语法：

select *, (select min(dt1) 
           from (select dt1 from t union select dt2 from t union select dt3 from t union select dt4 from t)a
           where a.dt1 > '1970-01-01') as DDt
from t