确定选择记录的OR语句？

Question

我在criteria表的记录中保存了标准，我用它来创建一个动态查询字符串，该字符串将查询source表，并将该查询的结果插入到destination表。我的目标是，如果条件与criteria表中的记录匹配，也会将destination表中的id插入source表。如果匹配了多个条件记录，我只需插入第一个条件。

WHERE子句是通过 OR'ing 将多个部分组合在一起构建的，并且每个部分内的条件都是 AND'ed 。如下所示：

insert into destinationTable(col1, col2, col3)
select col1, col2, col3
from sourceTable
where
--' begin generated code'
   (a = 525 and b = 324 and c = 4523) -- 'from criteria record 1'
or (d = 'asdf' and e = 3.43) -- 'from criteria record 2'
or (f = 234523 and g = 9823742) -- 'from criteria record 3'
etc...
--' end generated code'

我需要找到一种方法来确定哪个是匹配条件的第一个OR部分，并在目标表中插入相应的条件id如何做到这一点？

Answer 1

您可以在Select子句中包含一个case语句，该语句将输出成功的第一个OR子句：

Select ...
    , Case
        When a = 525 And b = 324 And C = 4523 Then Criteria_Row_1_Pk
        When d = 'asdf' and e = 3.43 Then Criteria_Row_2_Pk
        ....
        End As SuccessClausePk

Answer 2

将union替换为union，并添加一个给出标准号

的列

select col1, col2, col3, 1
from sourceTable
where
--' begin generated code'
   (a = 525 and b = 324 and c = 4523) -- 'from criteria record 1'
union all
select col1, col2, col3, 2
from sourceTable
where (d = 'asdf' and e = 3.43) -- 'from criteria record 2'
union all
select col1, col2, col3, 3
from sourceTable
where (f = 234523 and g = 9823742) -- 'from criteria record 3'
etc...

Answer 3

除非可能存在可以提供所涉及的所有列的索引，否则表可能会被完全扫描。由于我们正在浏览所有记录，因此您也可以执行之前的确定过滤。

SELECT col1, col2, col3, Which
FROM
(
    select col1, col2, col3,
    CASE
    --' begin generated code'
    WHEN 
       (a = 525 and b = 324 and c = 4523) -- 'from criteria record 1'
    THEN 1
    WHEN
       (d = 'asdf' and e = 3.43) -- 'from criteria record 2'
    THEN 2
    WHEN
       (f = 234523 and g = 9823742) -- 'from criteria record 3'
    THEN 3
    --' end generated code'
    END Which
    from sourceTable
) SQ
WHERE Which is not null -- remove where it didn't match any criteria

表单可预测且足够一致，足以代码生成友好