[英]Apply Mapping of Key-Value pair in Snowflake SQL
我有這張表:
Table_1:
KeyValue, Month
1, Oct,
3, Nov,
4, Sep,
5, Jan
直到“十二月”。 我希望這個故事用作另一個表查詢的字典。 所以,如果我給出一個案例查詢,我得到的日期比這個月的月份應該被 Table_1 的 KeyValue 替換。 例如:
CAST(Month(getdate()) as int)
gives "Sep" but the output should be
"4" because it is KeyValues of 'Sep' in Table_1
在雪花中如何實現?
它只是一個在字典表中查找的子查詢:
SELECT *, (SELECT t1.KeyValue FROM Table_1 AS t1 WHERE t1.Month = MONTH(GETDATE()))
FROM some_tab;
也可以實現為 JOIN:
SELECT s.*, t1.KeyValue
FROM some_tab AS s
JOIN Table_1 AS t1
ON t1.Month = s.<col_name>;
當您可以通過簡單的連接來實現它時,我試圖了解這里的復雜性。
month_mapping
視為您的具有鍵值對的映射表,並將dataset
視為您要加入的另一個表
with month_mapping (month_key, month_value) as
(
select * from
(
values (1, 'Oct')
, (3, 'Nov')
, (4, 'Sep')
, (5, 'Jan')
)
)
, dataset (actual_date) as
(
select * from
values (current_timestamp)
, (dateadd(month, 1, current_timestamp))
, (dateadd(month, 2, current_timestamp))
, (dateadd(month, 4, current_timestamp))
, (dateadd(day, 2, current_timestamp))
, (dateadd(day, -10, current_timestamp))
, (dateadd(day, 20, current_timestamp))
)
select ds.actual_date, mm.month_key, mm.month_value
from dataset ds
inner join month_mapping mm
on upper(mm.month_value) = upper(monthname(ds.actual_date))
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