dbplyr 不明确的列名

Question

我正在使用ODBC 和dbplyr 加入两个相对简单的表。但是，我的加入密钥出现错误，它抛出了ambiguous column name error。 dplyr 连接通常不会发生这种情况，我不知道如何使用 a.key = b.key，使用 dbplyr。

Error: nanodbc/nanodbc.cpp:1655: 42000: [Microsoft][ODBC SQL Server Driver][SQL Server]Ambiguous column name 'Calendar_key'.  [Microsoft][ODBC SQL Server Driver][SQL Server]Statement(s) could not be prepared. 
<SQL> 'SELECT "Calendar_key", "Organization_key", "Product_Key", "Promotion_Key", "Shift_Key", "ETL_source_system_key", "Pack_Size", "Qty_Sold", "Inv_Unit_Qty", "Extended_Cost", "Extended_Purchase_Rebate", "Extended_Sales_Rebate", "Extended_Sales", "Ent_Source_Hdr_Key", "Ent_Source_Dtl_Key", "Day_Date", "Day_Of_Week_ID", "Day_Of_Week", "Holiday", "Type_Of_Day", "Calendar_Month_No", "Calendar_Month_Name", "Calendar_Qtr_No", "Calendar_Qtr_Desc", "Calendar_Year", "Fiscal_Week", "Fiscal_Period_No", "Fiscal_Period_Desc", "Fiscal_Year"
FROM "Item_Sales_Fact" AS "LHS"
LEFT JOIN "calendar" AS "RHS"
ON ("LHS"."Calendar_key" = "RHS"."calendar_key")

这是下面的代码块：我的连接被称为 con

con <- dbConnect(odbc(),
                 Driver = "SQL Server",
                 Server = "192.168.139.1",
                 Database = "pdi_warehouse_2304_01",
                 UID = XXXX,
                 PWD = XXXX,
                 Port = 1433)

item.sales <- tbl(con, "Item_Sales_Fact")
calendar <- tbl(con, "calendar")
organization <- tbl(con, "Organization")

test.df <- item.sales %>%
  left_join(calendar, by = c("Calendar_key" = "calendar_key")) %>%
  collect()

Answer 1

dbplyr 生成的SQL 不正确，因为Calendar_key 可以来自RHS 或LHS，因为SQL 不区分大小写，并且与R 相反并没有区别在Calendar_key 和calendar_key 之间：

SELECT "Calendar_key", ...

问题似乎来自这样一个事实，虽然SQL 不区分大小写，但SQL Server 处理区分大小写的列名。

一种解决方法是重命名两个键之一以获得完全相同的区分大小写的名称：

item.sales <- tbl(con, "Item_Sales_Fact")
calendar <- tbl(con, "calendar") %>% rename(Calendar_key = calendar_key)

test.df <- item.sales %>%
  left_join(calendar, by = c("Calendar_key" = "Calendar_key")) %>%
  collect()