select
	exp_id ,
	usercnt1 as exp_user_cnt,
	case
		when usercnt1 = 0 then 0
		else retain1 / usercnt1
	end as value
from
	(
	select
		exp_id,
		count(case when retain_days = 1 then uid end) as usercnt1,
		cast(count(case when retain_days = 1 and is_retain = 'true' then uid end) as double) as retain1
	from
		(
		select
			exp_id,
			day,
			uid,
			retain_days,
			is_retain
		from
			c_dm.dm_grw_user_sd
		where
			day >= '2021-11-29'
			and day <= '2021-12-01'
			and layer_id = 2010
		order by
			exp_id,
			uid,
			retain_days,
			day
		limit 1 by exp_id,
		uid,
		retain_days ) a
	group by
		exp_id )
order by
	exp_id

CCJSqlParserUtil.parse(sql)

net.sf.jsqlparser.JSQLParserException: Encountered unexpected token: "by" "BY"
    at line 33, column 11.

Was expecting one of:

    ")"
    "EXCEPT"
    "FOR"
    "INTERSECT"
    "MINUS"
    "UNION"
	at net.sf.jsqlparser.parser.CCJSqlParserUtil.parseStatement(CCJSqlParserUtil.java:190)
	at net.sf.jsqlparser.parser.CCJSqlParserUtil.parse(CCJSqlParserUtil.java:63)
Caused by: net.sf.jsqlparser.parser.ParseException: Encountered unexpected token: "by" "BY"
    at line 33, column 11.