Question

我在带有参数@firstId和@secondId

的商店过程中有如下sql server查询

IF @firstId = ''
begin

SELECT DISTINCT x, y =
FROM t1
LEFT OUTER JOIN t2 ON t1.id = t2.id AND t2.id = @secondId
ORDER BY t1.somecolumn

END
ELSE
BEGIN

SELECT DISTINCT x, y =
FROM t1
LEFT OUTER JOIN t2 ON t1.id = t2.id AND t2.id = @secondId
AND t1.id = @firstId
ORDER BY t1.somecolumn
END

我对sqlite很新，并尝试在sqlite中使用case语句编写上述查询，如sqlite文档中所建议的那样，但到目前为止还无法实现相同的目的。我希望实现类似下面的内容或更好的查询。

CASE WHEN @firstId = '' THEN (CHOOSE FIRST SELECT STATEMENT) ELSE (CHOOSE SECOND SELECT STATEMENT) END

我想把原始的sql查询拆分成sqlite中的两个select语句，并根据c＃代码库文件中处理的条件调用相应的查询，如下所示，但不确定这是不是很好。

if(firstId == string.empty)
{
//call the first select statement
}
else
{
//call the second select statement
}

我不想将商店流程拆分为两个单独的查询。任何帮助表示赞赏。

Answer 1

你可以一气呵成。以上2个陈述相当于：

SELECT DISTINCT x, y
FROM t1
LEFT OUTER JOIN t2 ON t1.id = t2.id AND t2.id = @secondId
                      AND (t1.id = @firstId OR  @firstId = '')
ORDER BY t1.somecolumn

在sqlite中替换以下查询

1 个答案: