一、date_format的用法

1. 作用

格式化日期时间，将日期按照自己想要的格式输出。

date_format(date, format)：date参数是合法的日期，format参数是规定日期输出的格式。

SELECT CURRENT_DATE AS time1, DATE_FORMAT(CURRENT_DATE, 'yyyyMMdd') AS time2;

--输出结果
time1		time2
2022-12-06	20221206

可参考Hive官网中 date_format() 函数的描述。

Letter	Date or Time Component	Presentation	Examples
`G`	Era designator	Text	`AD`
`y`	Year	Year	`1996`; `96`
`Y`	Week year	Year	`2009`; `09`
`M`	Month in year	Month	`July`; `Jul`; `07`
`w`	Week in year	Number	`27`
`W`	Week in month	Number	`2`
`D`	Day in year	Number	`189`
`d`	Day in month	Number	`10`
`F`	Day of week in month	Number	`2`
`E`	Day name in week	Text	`Tuesday`; `Tue`
`u`	Day number of week (1 = Monday, …, 7 = Sunday)	Number	`1`
`a`	Am/pm marker	Text	`PM`
`H`	Hour in day (0-23)	Number	`0`
`k`	Hour in day (1-24)	Number	`24`
`K`	Hour in am/pm (0-11)	Number	`0`
`h`	Hour in am/pm (1-12)	Number	`12`
`m`	Minute in hour	Number	`30`
`s`	Second in minute	Number	`55`
`S`	Millisecond	Number	`978`
`z`	Time zone	General time zone	`Pacific Standard Time`; `PST`; `GMT-08:00`
`Z`	Time zone	RFC 822 time zone	`-0800`
`X`	Time zone	ISO 8601 time zone	`-08`; `-0800`; `-08:00`

获取年月日时分秒：

SELECT DATE_FORMAT('2022-07-04 15:10:25', 'yyyy-MM-dd HH:mm:ss') AS time;