spark-sql 笔记

1、get_json_object 返回json键值

select get_json_object('{"a":"dd"}','$.a');
dd
select get_json_object('{"b":"c"}','$.a');//json 键 “b” ≠ a 这里没有返回值
➜

select get_json_object('{"c":"d"}','$.c');//json 键 “c” = c 这里返回值 d
➜
get_json_object({"c":"d"}, $.c)
d

select get_json_object('{"ac":"d"}','$.ac'); //主键 ac
➜
get_json_object({"ac":"d"}, $.ac)
d

get_json_object({"a":{"B":"c"}}, $.a)

{"B":"c"}

2、substring_index

select substring_index('www.33.vv','',3);

空串返回空；

select substring_index('www.33.vv','e',3);

不存在，就返回原始串 www.33.vv

select substring_index('www.33.vv','.',3);

超出，就返回原始串 www.33.vv

select substring_index('www.abcd.ory','.',1);

正常情况：www

3、hex 、unhex 、decode(... , 'utf-8')

select hex('spark sql');
hex(spark sql)
返回：737061726B2073716C

select decode(unhex('737061726B2073716C'),'utf-8');
返回：
decode(unhex(737061726B2073716C), utf-8)
spark sql

4、to_json

select to_json(named_struct('a','1','b','1'));
➜
structstojson(named_struct(a, 1, b, 1))
{"a":"1","b":"1"}

----------------

select to_json(named_struct('a','b','c')); //键值不成对就会报错

➜
StatementCallback; uncategorized SQLException for SQL [select to_json(named_struct('a','b','c'))]; SQL state [null]; error code [0];

----------------

select to_json(named_struct('time',to_timestamp('2015-08-26','yyyy-MM-dd')),map('timestampFormat','dd/MM/yyyy'));
➜
structstojson(named_struct(time, to_timestamp('2015-08-26', 'yyyy-MM-dd')))
{"time":"26/08/2015"}

------------------------------------

select to_json(named_struct('time',to_timestamp('2015-11-12 22:10:30','yyyy-MM-dd HH:mm:ss')) );

➜

structstojson(named_struct(time, to_timestamp('2015-11-12 22:10:30', 'yyyy-MM-dd HH:mm:ss')))
{"time":"2015-11-12T22:10:30.000+08:00"}

-------------------------

select to_json(named_struct('time',to_timestamp('2015-12-11 10:23:01','yyyy-MM-dd HH:mm:ss')), map('timestampFormat','yyyy-HH-dd HH:mm:ss') );

➜

structstojson(named_struct(time, to_timestamp('2015-12-11 10:23:01', 'yyyy-MM-dd HH:mm:ss')))
{"time":"2015-10-11 10:23:01"}

map('timestampFormat','yyyy-HH HH:mm:ss') ); map 函数可以有选择性的显示日期格式

{"time":"2015-10 10:23:01"}，输出，年月和时分秒；

-------------------------

两项报错：
to_timestamp('2015-11-10 XXXXX',日期时间格式 )，函数，如果没有写日期格式就会报错
select to_json(named_struct('time',to_timestamp('2015-11-11 12:23:12')) , map('timestampFormat','yyyy-MM-dd HH:mm:ss') );
select to_json(named_struct('time',to_timestamp('2015-11-11') ) );
报错：StatementCallback; uncategorized SQLException for SQL [select

---------------------

5 、current_timestamp/now()获取当前时间

select current_timestamp as a , now() as b;

➜

a	b
1627527952763	1627527952763

select current_date ;获取日期的年月日

current_date()
2021-07-29

select day(current_date) 或者 select day('2021-07-29')返回29，代表29号；

如果current_date 获取的日期是 2021-07-29 ，那么day(current_date)返回的结果：29；

------------------

select dayofweek('2021-07-29') ,

报错信息：StatementCallback; uncategorized SQLException for SQL

如果日期直接输入字符串，这样查询就会报错；

---------------

获取年份下当前第几周，从当年的第一天开始到当天之间的总天数除以 7 得出的一个数据 N ；余数如果大于3 ，那么返回 N+ 1 ；如果余数小于3 那么返回 N；

select weekofyear(current_date); 或者 select weekofyear('2021-07-29');

返回结果：30；

select weekofyear('2021-01-07') as d2;

1月7号，刚好第一周

d2
1

➜select weekofyear('2021-01-08') as d2;

1月8号，属于第二周，但是8-7<3; 所以还是1；

d2
1

➜select weekofyear('2021-01-11') as d2;➜

d2
2

select weekofyear('2021-01-15') as d2;

15 - 7 * 2 < 3 这里返回2；

d2
2

select weekofyear('2021-01-18') as d2;

d2
3

------------

select dayofyear('');

select dayofyear(current_date) as dd,dayofyear('2021-07-29') as de;

dd	de
210	210

------------

CAST(month(current_date()) AS STRING) 数值转换为字符串；

---------------------------------

年月日，时分秒；

select
year(current_date) as year,
month(current_date) as month,
day(current_date) as day,
hour(current_timestamp) as hour,
minute(current_timestamp) as minute,
second(current_timestamp) as second;

select
year(current_date) as year,
(
case length(cast( month(current_date) as string) )
when 1
then concat( '0' , cast( month(current_date) as string) )
else month(current_date)
end
) as month,
day(current_date) as day,
(
case length(hour(current_timestamp))
when 1
then concat( '0' , cast ( hour(current_timestamp) as string) )
else hour(current_timestamp)
end
) as hour,
(
case length(minute(current_timestamp))
when 1
then concat( '0' , cast( minute(current_timestamp) as string) )
else minute(current_timestamp)
end
) as minute,
(
case length(second(current_timestamp))
when 1
then concat( '0' , cast( second(current_timestamp) as string) )
else second(current_timestamp)
end
) as second;

--------------------

select date_format(current_date,'yyyy') as year,
date_format(current_date,'MM') as MM,
date_format(current_date,'dd') as DD,
date_format(current_timestamp,'HH') as HH,
date_format(current_timestamp,'mm') as monute,
date_format(current_timestamp,'ss') as ss
;

---------------------

当年到当天的天数和周数；

select dayofyear(current_date) as days,weekofyear(current_date) as weeks;

-----------------------

获取当前时间的年月日时分秒；

select
from_unixtime(CAST(current_timestamp() AS BIGINT), 'yyyy-MM-dd HH:mm:ss') as ymd1 ,
from_unixtime(CAST(current_timestamp() AS BIGINT)) as ydm2
;