sqldf在使用子查詢時給出錯誤

Question

我正在嘗試使移動平均值到星期幾，因爲我正在使用sql查詢。 據幀是

和sqldf代碼：

ma_782 = sqldf("SELECT 
     t1.Id_indicator, t1.Hour, 
( 
    select SUM(t2.Value)/COUNT(t2.Value)         
    FROM max_value_782 AS t2 
    WHERE 
     t1.Hour = t2.Hour and 
      weekdays.Date(t1.Date) = weekdays.Date(t2.Date) 
      and DATEDIFF(t1.Date, t2.Date) BETWEEN 1 AND 42   
) AS 'MA_by_weekday' 
FROM max_value_782 AS t1 ;") 

這給了錯誤的rsqlite_send_query

錯誤（康涅狄格州@ PTR，語句）：近 「（」：語法錯誤

whi它適用於簡單的選擇：

sqldf("select * from max_value_782") 

Answer 1

考慮替換weekdays.方法，因爲此語法假定表限定符。由於默認情況下，sqldf使用SQLite方言，請使用strftime來比較工作日。此外，單引號用於字符串文字，不包含表/字段標識符。 SQLite可以使用括號，反引號或雙引號，如果不使用保留字/特殊字符，則可以使用none。

ma_782 = sqldf("SELECT t1.Id_indicator, t1.Hour, 
         (SELECT AVG(t2.Value) 
          FROM max_value_782 AS t2 
          WHERE t1.Hour = t2.Hour 
          AND strftime('%w', t1.Date) = strftime('%w', t2.Date) 
          AND (t2.Date - t2.Date) BETWEEN 1 AND 42   
         ) AS MA_by_weekday 
       FROM max_value_782 AS t1;")