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wuwukai007
V2EX  ›  Python

Sqlalchemy 如何实现 case + subquery 嵌套 subquery

  •  
  •   wuwukai007 · Sep 8, 2022 · 2425 views
    This topic created in 1365 days ago, the information mentioned may be changed or developed.
    select case
               when user.id > 10000 then
                   (select true_flag
                    from score
                    where created_time = (
                        select max(created_time)
                        from score
                        where user.id = score.user_id
                    ))
               when user.id <= 10000 then
                   (select true_flag
                    from score_bak
                    where created_time = (
                        select max(created_time) from score_bak where user.id = score_bak.user_id
                    ) 
                   ) 
            end true_flag
    from user;
    
    • 使用 case 函数 最后会变成 select true_flag from user,score 把两个表连表了
    Supplement 1  ·  Sep 8, 2022

    真的瑞了,投降了,使用原生sql

    from sqlalchemy import text,select,column
    sql = text(sql)
    sql = sql.columns(column('true_flag'))
    subquery = select(sql.selected_columns.true_flag).select_from(sql.subquery())
    
    3 replies    2022-09-09 09:58:16 +08:00
    xhzhang
        1
    xhzhang  
       Sep 8, 2022
    这个你可以把 case 语句放到 where 的 join 条件中,用 user join 两张表,添加不同的 join 条件,select 语句就按照你现在的逻辑取数就可以
    xhzhang
        2
    xhzhang  
       Sep 8, 2022
    select xxx from user join score on user.id = score.user_id and user.id > 10000 join score_bak on user.id = score.user_id and user.id <= 10000
    joApioVVx4M4X6Rf
        3
    joApioVVx4M4X6Rf  
       Sep 9, 2022
    试了一下好像还真是和楼主说的会变成连表
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