PLSQL：CASE 结果中的多个值

Question

我正在为我的 PLSQL 查询based on this answer（以及许多其他类似的）动态设置要排序的列。我想添加一个默认情况，它按三列排序。

这是我的尝试：

-- ... long SQL query
--      ps_global_order is the column to sort on, passed in to stored procedure.
--      ps_global_order_dir is the direction to sort on, similarly passed in. 
order by 
  case 
    -- this does not compile (00905 missing keyword):
    when ps_global_order is null then name, phone, email 
    -- this compiles, but I need it on the three columns:
    -- when ps_global_order is null then name  
  end,
  case
    when ps_global_order_dir <> 'ASC' then ''
    when ps_global_order like 'name' then name
  end,
  case
    when ps_global_order_dir <> 'ASC' then ''
    when ps_global_order like 'phone' then phone
  end,
  case
    when ps_global_order_dir <> 'ASC' then ''
    when ps_global_order like 'email' then email
  end,
  case
    when ps_global_order_dir <> 'DESC' then ''
    when ps_global_order like 'name' then name
  end,
  case
    when ps_global_order_dir <> 'DESC' then ''
    when ps_global_order like 'phone' then phone
  end,
  case
    when ps_global_order_dir <> 'DESC' then ''
    when ps_global_order like 'email' then email 
  end

一切正常，但我想指定这三列进行排序。

CASE 语句可以做到这一点吗？我必须求助于动态 SQL 还是有我遗漏的解决方法？

Answer 1

这样做：

-- ... long SQL query
--      ps_global_order is the column to sort on, passed in to stored procedure.
--      ps_global_order_dir is the direction to sort on, similarly passed in. 
order by 
  case 
    when ps_global_order is null then name
    else null
  end,
  case
    when ps_global_order is null then phone
    else null
  end,
  case
    when ps_global_order is null then email
    else null
  end,
  case
    when ps_global_order_dir <> 'ASC' then null
    when ps_global_order like 'name' then name
  end,
  case
    when ps_global_order_dir <> 'ASC' then null
    when ps_global_order like 'phone' then phone
  end,
  case
    when ps_global_order_dir <> 'ASC' then null
    when ps_global_order like 'email' then email
  end,
  case
    when ps_global_order_dir <> 'DESC' then null
    when ps_global_order like 'name' then name
  end,
  case
    when ps_global_order_dir <> 'DESC' then null
    when ps_global_order like 'phone' then phone
  end,
  case
    when ps_global_order_dir <> 'DESC' then null
    when ps_global_order like 'email' then email 
  end

请注意，我已将所有出现的 '' 替换为 NULL，这更清楚 IMO。

Answer 2

我讨厌这么快回答我自己的问题，但我想通了：

order by 
    case  when nvl(ps_global_order, ' ') = ' ' then name end,
    case  when nvl(ps_global_order, ' ') = ' ' then phone end,
    case  when nvl(ps_global_order, ' ') = ' ' then email end,
    case
        when ps_global_order_dir <> 'ASC' then ''
    -- continues...

This answer 提供了很大帮助，但它被隐藏在 Google 搜索结果中。不过，没有逗号的情况下它是如何工作的却让我望而却步。