使用每个kdb从另一个表的列表中查找不同的值 [英] find distinct values from a list in another table using each kdb

问题描述

我已经找到tb表中event =`OvernightOrder的b_market_order_no，无论使用哪种方法

I have found distinct b_market_order_no where event=`OvernightOrder from tb table, using either method

b_mkt_lst: select `g#b_market_order_no from tb where event=`OvernightOrder
b_mkt_lst: select distinct b_market_order_no from tb where  event=`OvernightOrder

对于该列表中具有b_market_order_no的所有记录，需要在另一个名为tbp的表中查找该b_market_order_no的b_orig_date，我尝试以下两种方法:

For all records that have a b_market_order_no in that list need to find the b_orig_date for that b_market_order_no in another table called tbp, I try these two methods:

select b_orig_date from tbp where b_market_order_no in b_mkt_lst
select b_orig_date from tbp each b_mkt_lst

第一个给我的长度不兼容，第二个不能识别b_orig_date，但是从tbp中选择b_orig_date"确实会返回结果.

First one gives me incompatible length the second does not recognize b_orig_date, but "select b_orig_date from tbp" does return results.

推荐答案

对数据进行一些假设:

q)t:([]c1:`a`b`c;c2:1 2 3)

/your length error is because you're comparing a list (b_market_order_no col) to a table (b_mkt_lst)
/similar to
q)select from t1 where c2 in select distinct c2 from ([]c2:1 3)
'length                        

/instead, use exec to extract a list (thus comparing a list to a list)
q)select from t1 where c2 in exec distinct c2 from ([]c2:1 3)
c1 c2
-----
a  1
c  3

/or turn the column(s) into a table to compare table to table
/(this is more useful when there's more than one column to compare)
q)select from t1 where ([]c2) in select distinct c2 from ([]c2:1 3)
c1 c2
-----
a  1
c  3

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