[英]How to get the minimum date of several columns, excluding nulls?
insert into table (col1, col2, col3, col4) values ('2015-01-01','2014-01-01', NULL, '2013-01-01')
I am looking for a function like this: 我正在寻找这样的功能:
select least_but_no_nulls(col1, col2, col3, col4) from table
result: '2013-01-01' 结果:“ 2013-01-01”
How can I get the minimum date of several columns, excluding nulls? 如何获取几列的最小日期,不包括空值?
Alas, least()
now returns NULL
if any arguments are NULL
. 唉, least()
现在返回NULL
,如果任何参数是NULL
。 You can use a giant coalesce: 您可以使用巨大的合并:
select least(coalesce(col1, col2, col3, col3),
coalesce(col2, col3, col4, col1),
coalesce(col3, col4, col1, col2),
coalesce(col4, col1, col2, col3)
)
Or, you can use some unlikely value in the future and nullif()
: 或者,您可以在将来使用一些不太可能的值和nullif()
:
select nullif(least(coalesce(col1, '9999-01-01'),
coalesce(col2, '9999-01-01'),
coalesce(col3, '9999-01-01'),
coalesce(col4, '9999-01-01'),
), '9999-01-01'
)
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