Sql Server - 如何获得最少的合格记录？

Question

如何根据我传递给查询的“年龄”获得最少的行数？

这个年龄不是表中minAge或maxage的一部分..

我的存储过程的例子

declare @MyAge int;
select @MyAge = 21;

select *
from Mytable
where ( AssuranceId = 9 and MemberTypeId = 1 )
and  (  @MyAge between MinAge and MaxAge ) -- obvious this will return nothing

- 但是我希望它能够在最小和最大年龄行返回那个带有空值的行 - 如果它确实找到一个符合条件的行

- 所以它应该返回行ID：16 或任何建议将不胜感激

Answer 1

declare @MyAge int;
select @MyAge = 21;

select *
from Mytable
where ( AssuranceId = 9 and MemberTypeId = 1 )
and  (isnull(@MyAge, 0) between isnull(MinAge, 0) and isnull(MaxAge, 200))

<强> UPD

如果您想要一个最具体的记录，您可以添加订单子句：

declare @MyAge int;
select @MyAge = 38;

select top 1 *
from Mytable t
where ( AssuranceId = 9 and MemberTypeId = 1 )
and  (isnull(@MyAge, 0) between isnull(MinAge, 0) and isnull(MaxAge, 200))
order by
  t.MinAge desc, t.MaxAge desc
;

这会给你一条MinAge = 38但没有空值的记录。

Answer 2

如果我理解正确，您的查询逻辑就是要保留@MyAge和MinAge之间的MaxAge所有记录，除非是那里没有记录，在这种情况下，您需要MinAge和MaxAge都是NULL的记录。我看不到在这里使用子查询。我在WHERE子句中有一个子查询，它检查是否有任何范围匹配记录。如果是，那么它会使用您之前的WHERE条件，如果没有，则会在年龄列上使用IS NULL支票。

SELECT *
FROM Mytable
WHERE (AssuranceId = 9 AND MemberTypeId = 1) AND TRUE =
    CASE WHEN (SELECT COUNT(*) FROM Mytable WHERE @MyAge BETWEEN MinAge AND MaxAge) > 0
        THEN (@MyAge >= MinAge AND @MyAge <= MaxAge)
        ELSE (MinAge IS NULL AND MaxAge IS NULL)
    END

在这种情况下，子查询的惩罚应该很小，因为它没有相关性。

Answer 3

有一个公用表表达式（cte），用于选择AssuranceId = 9和MemberTypeId = 1的行。

使用该cte，如果BETWEEN条件为真，则返回该行。 OR如果根本不存在这样的行。

with cte as
(
    select *
    from Mytable
    where AssuranceId = 9 and MemberTypeId = 1
)
select * from cte
where (isnull(@MyAge, 0) between isnull(MinAge, 0) and isnull(MaxAge, 200)
       AND (MinAge is not null or MaxAge is not null))
   OR NOT EXISTS (select * from cte 
                  where isnull(@MyAge, 0) between isnull(MinAge, 0) and isnull(MaxAge, 200)
                    and (MinAge is not null or MaxAge is not null))

Answer 4

试试这个..

select top (1) * -- you might be excepting only one row here by preference
from Mytable
where ( AssuranceId = 9 and MemberTypeId = 1 )
and  ( -- added 
        (@MyAge between MinAge and MaxAge ) -- first preference
       OR( MinAge IS NULL AND MaxAge<=@MyAge) --Second preference
       OR( MaxAge IS NULL AND MinAge>=@MyAge) -- third preference
       OR(MinAge IS NULL AND MaxAge Is NUll) -- Last preference
   )-- added 

Answer 5

Try this:

declare @MyAge int;
select @MyAge = 21;
select * from Mytable
where ( AssuranceId = 9 and MemberTypeId = 1 )
and  (MinAge is NULL OR MinAge <= @MyAge) AND (MaxAge is NULL OR MaxAge >= @MyAge)