OleDb 选择命令返回一个空列

Question

我的数据库中有两个已保存的查询，名为 Free_Cash_Flow 和 Quarterly_Growth_Rates。它们显示在这里：

Free_Cash_Flow:

Quarterly_Growth_Rates:

当我使用这段代码时：

SELECT * _
FROM Free_Cash_Flow AS C _
INNER JOIN Quarterly_Growth_Rates AS G _
ON (C.Ticker = G.Ticker) AND ((IIF(C.Period = 4, C.Year + 1, C.Year)) = G.Year) AND ((IIF(C.Period = 4, 1, C.Period + 1)) = G.Qtr)

这是返回的：

Free_Cash_Flow 列为空白。但正如您在Free_Cash_Flow 表中看到的那样，该列中有数据。为什么没有被拉入新表？我用其他类似格式的表运行这个查询，一切都很好。有什么建议吗？

其他信息

我想补充一点，Free_Cash_Flow 列是使用其各自已保存查询的 SQL 语句中的公式填充的。我认为这可能与我的问题有关。我真的被困在这里，我迫切需要弄清楚这一点。

下面是包含用于 Free_Cash_Flow 保存查询的 SQL 语句的代码：

变量：

Dim Calculation = “Free_Cash_Flow”

Dim Formula = “(SELECT (SUM(su.Net_Cash_Flow_Operating) - SUM(su.Capital_Expenditures)) _
FROM (SELECT Ticker, [Year], Period, Net_Cash_Flow_Operating, Capital_Expenditures _
FROM Cash_Flow_Statements UNION ALL SELECT Ticker, [Year] + 1, Period - 4, Net_Cash_Flow_Operating, Capital_Expenditures _
FROM Cash_Flow_Statements) su _
WHERE su.Ticker = c.Ticker AND su.[Year] = c.[Year] AND (su.Period Between c.Period - 3 And c.Period))”

Dim Where_Statement = "WHERE i.Period < 5"

SQL 语句：

"CREATE PROC " & Calculation & " AS SELECT i.Ticker, i.[Year], i.Period, " & Formula & " AS " & Calculation & " _
FROM (Income_Statements AS i _
INNER JOIN Balance_Sheets AS b _
ON (i.Ticker = b.Ticker) AND (i.[Year] = b.[Year]) AND (i.Period = b.Period)) _
INNER JOIN Cash_Flow_Statements AS c ON (b.Ticker = c.Ticker) AND (b.[Year] = c.[Year]) AND (b.Period = c.Period) " & Where_Statement & ""

Answer 1

不知道具体原因，但通常不首选使用“*”，但如果您明确查询命名列，您可能会得到更好/正确的答案，例如

select 
      C.Ticker,
      C.Year,
      C.Period,
      C.Free_Cash_Flow,
      G.Year as GrowthYear,
      G.Period as GrowthPeriod 
   from ....

它可能会感到困惑，因为表名与列相同并忽略它。通过分别使用“C”和“G”别名限定列，可能会满足您的需求。

Answer 2

这可能与您的 JOIN 无关。我想知道Free_Cash_Flow 是否属于OLEDB 无法理解的类型。看起来它在 Open Office 中是作为货币价值的，对吧？您是否知道 OLEDB 完全可以看到该值？尝试一个更简单的查询，例如

SELECT C.Free_Cash_Flow FROM Free_Cash_Flow AS C

看看有没有什么结果。

Answer 3

理论上，它没有理由不工作，除非列名与表名相同。也许您的数据库引擎对此感到困惑，请尝试重命名。

Answer 4

重命名时需要指定需要的列，如下面的C&G：

SELECT C.*, G.* _
FROM Free_Cash_Flow AS C _
INNER JOIN Quarterly_Growth_Rates AS G _
ON (C.Ticker = G.Ticker) AND ((IIF(C.Period = 4, C.Year + 1, C.Year)) = G.Year) AND ((IIF(C.Period = 4, 1, C.Period + 1)) = G.Qtr)

Answer 5

您是否尝试过将最后一部分更改为 WHERE 并查看返回的内容？

WHERE ((IIF(C.Period = 4, C.Year + 1, C.Year)) = G.Year) AND
      ((IIF(C.Period = 4, 1, C.Period + 1)) = G.Qtr)

Answer 6

尝试像下面这样替换表名并检查 Quarterly_Growth_Rates 列是否出现，如果该列也没有出现，那么可能是名称相同的问题。

SELECT * _
FROM Quarterly_Growth_Rates AS G _ INNER JOIN Free_Cash_Flow AS C _ON (G.Ticker = C.Ticker) AND (G.Year = (IIF(C.Period = 4, C.Year + 1, C.Year))) AND (G.Qtr = (IIF(C.Period = 4, 1, C.Period + 1)))