0

如果我写这样的查询：

with foo as (
    select
        'foo' as name,
        1 as value
    union all select
        'foo', 2
    union all select
        'foo', 3
    union all select
        'foo', 4
), bar as (
    select
        'bar' as name,
        3 as value
    union all select
        'bar', 4
    union all select
        'bar', 5
    union all select
        'bar', 6
)
select
    f.name,
    b.value,
    b.name
from
    foo as f
full outer join
    bar as b
    on b.value = f.value;

我明白了：

name        value    name
foo         (null)  (null)
foo         (null)  (null)
foo         3       bar
foo         4       bar
(null)      5       bar
(null)      6       bar

这是我所期望的。但是，如果我尝试使用像这样的表值函数做类似的事情：

with allSizes as (
        select cast('120X60' as character varying) as size
        union all select '160X600'
        union all select '1X1'
        union all select '300X250'
        union all select '728X90'
        union all select '88X32'
        union all select 'PEEL'
)
select
        msd.region,
        msd.market,
        s.size,
        msd.target,
        msd.actual
from 
        marketdata('2013-01-05') as msd
full outer join
        allSizes as s
        on s.size = msd.size
where
        msd.market = 'Foo, USA';

wheremarketdata()是一个表值函数，我没有得到与函数size中不存在的列相对应的空行marketdata()。为什么不？

4

1 回答 1

3

这是因为：

where
        msd.market = 'Foo, USA';

它产生full outer join然后过滤掉不存在于的行marketdata()（因为它们有msd.market= NULL）

您可以将查询更改为：

with allSizes as (
        select cast('120X60' as character varying) as size
        union all select '160X600'
        union all select '1X1'
        union all select '300X250'
        union all select '728X90'
        union all select '88X32'
        union all select 'PEEL'
)
select
        msd.region,
        msd.market,
        s.size,
        msd.target,
        msd.actual
from 
        (select marketdata('2013-01-05')
         where  market = 'Foo, USA') as msd
full outer join
        allSizes as s
        on s.size = msd.size;

或者干脆重写

where
        msd.market = 'Foo, USA' OR msd.market IS NULL;

如果marketdata()不返回任何行msd.market IS NULL。

于 2013-01-08T16:50:52.523 回答