Snowflake SPLIT_PART 函数不返回 Null 值

Question

下面是 JSON 文件中的示例数据

'Desktop::abc:voip::GET STARTED' 作为 Col1

当我运行 Snowflake 中的以下查询时，second_value 的值显示为空白而不是 NULL 值。我如何获得此示例数据的 NULL 值

select  'Desktop::abc:voip::GET STARTED' as Col1
        split_part(:Col1 :: String, ':', 1) as First_Value,
        split_part(:Col1 :: String, ':', 2)  as Second_Value,
        split_part(:Col1 :: String, ':', 3) as Third_Value,
        split_part(:Col1 :: String, ':', 4) as Fourth_Value;

输出如下

Answer 1

您可以使用 NULLIF() 将零长度字符串强制转换为 NULLS。例如：

select  'Desktop::abc:voip::GET STARTED' as Col1,
NULLiF(split_part(Col1 :: String, ':', 1),'') as First_Value,
NULLiF(split_part(Col1 :: String, ':', 2),'') as Second_Value,
NULLiF(split_part(Col1 :: String, ':', 3),'') as Third_Value,        
NULLiF(split_part(Col1 :: String, ':', 4),'') as Fourth_Value

Snowflake SPLIT_PART 函数不返回 Null 值

Snowflake SPLIT_PART Function not returning Null values

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