Question

如果我的查询1无法获取结果，我需要引入一个虚拟行。

select column1,column2,... from <ActualTable> Where condition='abc'... (1)
Union
select "dummy col1","dummy col2"..... from <dummy table> where col1 NOT IN (select column1 from
<ActualTable> where condition = 'abc'..)                               (2)

使用上面的查询，如果查询1获取结果查询2不会。如果查询1没有结果，那么我会得到一个虚拟行。

有没有其他方法可以在Sybase中实现相同的结果？

Answer 1

临时表，如果“ActualTable”给出＆gt; 1行

select column1,column2,... INTO #temp
from <ActualTable>
Where condition='abc'... (1)

IF @@ROWCOUNT = 0
    select "dummy col1","dummy col2"..... INTO #tmp
    from <dummy table>

-- #temp will exist now

INSERT #temp
select column1,column2,...
from <AnotherTable>
Where condition='abc'... (1)

IF @@ROWCOUNT = 0
    INSERT #temp
    select "dummy col1","dummy col2".....
    from <dummy table>

... 
SELECT * FROM #tmp

Answer 2

试试这个：

select top 1 * from
(
select 0,column1,column2,... from <ActualTable> Where condition='abc'... (1)
Union
select 1,"dummy col1","dummy col2"..... from <dummy table> 
order by 1
)

如果第一次查询成功，您将获得它，如果没有，则返回第二次

在sybase查询中引入虚拟行

2 个答案: