SQL 会计日期、平面文件、痛苦

Question

使用 sqlite3、python

我有一个蹩脚的遗留文件legacy_sales：

item | year | week | mon | tue | wed | thu | fri | sat |sun 
4444   2011     29    10    0     4    15     18    25   30

我有一个很棒的新文件sales（这是上面“mon”条目的示例）：

item | units |     date
4444   10       2011-03-14

我在另一个表中有会计年度的开始日期 fiscal

year | start_date
2011   2010-08-30

有了这些信息，实现这一目标的最佳和最有效的方法是什么：

insert into sales from (insert magic here) 

不使用任何 UDF...

有这样的胡言乱语的经验吗？

Answer 1

insert into sales from (
    -- here be magic
    select  item, units, DATEADD(day, DayInYear, start_date)
    from    (
        select  item,
                year,
                (week - 1) * 7 + 0 as DayInYear,
                mon as Units
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 1, tue
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 2, wed
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 3, thu
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 4, fri
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 5, sat
        from    legacy_sales
        union all
        select  item, year, (week - 1) * 7 + 6, sun
        from    legacy_sales
        ) ls
        inner join fiscal on
            fiscal.year = ls.year
)

Answer 2

从：legacy_sales 转换

item | year | week | mon | tue | wed | thu | fri | sat |sun 
4444   2011     29    10    0     4    15     18    25   30

为：sales

item | units |     date
4444   10       2011-03-14

需要用英语 python 编写：

for row in legacy_sales:
    year = row['year']
    week = row['week']
    for day_name in "mon | tue | wed | thu | fri | sat |sun".split(" | "):
        some how turn (year, week, day_name) into year_month_day
        insert into sales values (row['item'], row[day_name], year_month_day)