多個條件下的案例陳述？

Question

我想檢查 mr.name 列，如果 mr.name 是 null，那么我必須將 mr.name 替換為 mr.ticket_no。 如何？ 可以使用 if else 或 case 嗎？

    select ROW_NUMBER() OVER(ORDER BY mr_user) sl_no,* from (select 
    mr.name as mr_no,
    coalesce(mr.user_id,0) as mr_user
    from stock_production_lot lot
    left join kg_grn grn on (grn.name = lot.grn_no)
    left join kg_department_indent mr on (mr.name = grn.mr_no)
    order by mr.user_id) main
    where  mr_user=65

當我這樣使用

case when mr.name is null then '' else mr.ticket_no = grn.mr_no as mr_no

它會拋出一個錯誤

如果 mr.name = null 意味着我必須替換 mr.name = mr.ticket_no。 我想檢查 mr.name 列，如果 mr.name 是 null 那么我必須將 mr.name 替換為 mr.ticket_no

Answer 1

您可以使用 coalesce() 將 null 替換為任何內容：

 select ROW_NUMBER() OVER(ORDER BY mr_user) sl_no,* from (select 
    coalesce(mr.name,mr.ticket_no)   as mr_no,
    coalesce(mr.user_id,0) as mr_user
    from stock_production_lot lot
    left join kg_grn grn on (grn.name = lot.grn_no)
    left join kg_department_indent mr on (mr.name = grn.mr_no)
    order by mr.user_id) main
    where  mr_user=65

但是，如果您對大小寫感到滿意，請按以下方式使用：

 select ROW_NUMBER() OVER(ORDER BY mr_user) sl_no,* from (select 
    (case when mr.name is null then mr.ticket_no else mr.name end)   as mr_no,
    coalesce(mr.user_id,0) as mr_user
    from stock_production_lot lot
    left join kg_grn grn on (grn.name = lot.grn_no)
    left join kg_department_indent mr on (mr.name = grn.mr_no)
    order by mr.user_id) main
    where  mr_user=65