在 Dataframes 中将日期从字符串转换为日期格式
问题描述：
我正在尝试使用 to_date 函数将字符串格式的列转换为日期格式，但它返回的是 Null 值.
I am trying to convert a column which is in String format to Date format using the to_date function but its returning Null values.
df.createOrReplaceTempView("incidents")
spark.sql("select Date from incidents").show()
+----------+
| Date|
+----------+
|08/26/2016|
|08/26/2016|
|08/26/2016|
|06/14/2016|
spark.sql("select to_date(Date) from incidents").show()
+---------------------------+
|to_date(CAST(Date AS DATE))|
+---------------------------+
| null|
| null|
| null|
| null|
日期列是字符串格式:
|-- Date: string (nullable = true)
答
使用 to_date 和 Java SimpleDateFormat.
Use to_date with Java SimpleDateFormat.
TO_DATE(CAST(UNIX_TIMESTAMP(date, 'MM/dd/yyyy') AS TIMESTAMP))
示例:
spark.sql("""
SELECT TO_DATE(CAST(UNIX_TIMESTAMP('08/26/2016', 'MM/dd/yyyy') AS TIMESTAMP)) AS newdate"""
).show()
+----------+
| dt|
+----------+
|2016-08-26|
+----------+