使用Scala中列出了星火SQL查詢

Question

我試圖運行下面的查詢：

val IgnoreList = List(""," ","0","-","{}","()","[]","null","Null","NULL","false","False","FALSE","NA","na","Na","n/a","N/a","N/A","nil","Nil","NIL") 
val df = sqlContext.sql(s"select userName from names where userName not in $IgnoreList") 

但是，這是行不通的。我也試過：

val IgnoreList = List(""," ","0","-","{}","()","[]","null","Null","NULL","false","False","FALSE","NA","na","Na","n/a","N/a","N/A","nil","Nil","NIL") 
sqlContext.udf.register("SqlList",(s: List[String]) => "('" + s.mkString("','") + "')") 
val df = sqlContext.sql(s"select userName from names where userName not in SqlList($IgnoreList)") 

但是這也行不通。有什麼建議麼？

Answer 1

您的第一次嘗試失敗，因爲它調用List的默認toString，它不會返回您需要的SQL有效語法。您的第二次嘗試失敗，因爲使用UDF構建SQL字符串沒有意義 - UDF將應用於記錄（或列），而不是創建字符串查詢。

您需要在第二個完成的格式化，在第一做了簡單的字符串插值結合：

val IgnoreList = List(""," ","0","-","{}","()","[]","null","Null","NULL","false","False","FALSE","NA","na","Na","n/a","N/a","N/A","nil","Nil","NIL") 
val condition = "('" + IgnoreList.mkString("','") + "')" 
val df = sqlContext.sql(s"select userName from names where userName not in $condition") 

BTW，可能會更清楚這樣格式化列表：

IgnoreList.map(s => s"'$s'").mkString(",")