如何按 Oracle SQL IN() 子句中的值顺序对结果数据进行排序答案

【问题标题】：How to order the result data by the order of values in an Oracle SQL IN() clause如何按 Oracle SQL IN() 子句中的值顺序对结果数据进行排序
【发布时间】：2016-12-19 10:46:28
【问题描述】：

当 SQL 返回结果时，我们需要按照将值传递给 SQL 的 IN() 子句的确切顺序对它们进行排序。

查询和结果：（HR 架构）

select EMPLOYEE_ID, FIRST_NAME
from EMPLOYEES
where EMPLOYEE_ID in ('151','149','145','147','155');

EMPLOYEE_ID FIRST_NAME         
----------- --------------------
        145 John                
        147 Alberto             
        149 Eleni               
        151 David               
        155 Oliver

但我们需要它们按 '151','149','145','147','155' 的顺序排列

预期输出

EMPLOYEE_ID FIRST_NAME         
----------- --------------------
        151 David               
        149 Eleni               
        145 John                
        147 Alberto             
        155 Oliver

在 MySQL 中，有 FIELD() 函数。如何在 Oracle 中实现这一点？

【问题讨论】：

标签： sql oracle sql-order-by

【解决方案1】：

在 Oracle 中，您可以在 PL/SQL 中编写自己的字段函数，也可以使用标准 SQL 的CASE WHEN：

select EMPLOYEE_ID, FIRST_NAME
from EMPLOYEES
where EMPLOYEE_ID in ('151','149','145','147','155')
order by case EMPLOYEE_ID 
  when '151' then 1
  when '149' then 2
  when '145' then 3
  when '147' then 4
  when '155' then 5;

这是一个派生表的替代方案：

select EMPLOYEES.EMPLOYEE_ID, EMPLOYEES.FIRST_NAME
from EMPLOYEES
join
(
  select '151' as EMPLOYEE_ID, 1 as POS from DUAL
  union all
  select '149' as EMPLOYEE_ID, 2 as POS from DUAL
  union all
  select '145' as EMPLOYEE_ID, 3 as POS from DUAL
  union all
  select '147' as EMPLOYEE_ID, 4 as POS from DUAL
  union all
  select '155' as EMPLOYEE_ID, 5 as POS from DUAL
) IDS ON IDS.EMPLOYEE_ID = EMPLOYEES.EMPLOYEE_ID
order by IDS.POS;

【讨论】：

【解决方案2】：

假设列表中的值是唯一的

select      e.EMPLOYEE_ID,e.FIRST_NAME

from                EMPLOYEES e

            join    (select  rownum as n,column_value as EMPLOYEE_ID 
                     from    table (SYS.ODCIVARCHAR2LIST ('151','149','145','147','155')) t
                    ) t  

            on      t.EMPLOYEE_ID =
                    e.EMPLOYEE_ID

order by    t.n

+-------------+------------+
| EMPLOYEE_ID | FIRST_NAME |
+-------------+------------+
| 151         | David      |
+-------------+------------+
| 149         | Eleni      |
+-------------+------------+
| 145         | John       |
+-------------+------------+
| 147         | Alberto    |
+-------------+------------+
| 155         | Oliver     |
+-------------+------------+

【讨论】：

【解决方案3】：

一种方法可能是使用提供顺序的属性来构建您的列表，并将其与您的表一起用于 JOIN。例如：

with yourList(EMPLOYEE_ID, position) as (
    select '151', 1 from dual union all
    select '149', 2 from dual union all
    select '145', 3 from dual union all
    select '147', 4 from dual union all
    select '155', 5 from dual
)
select EMPLOYEE_ID, FIRST_NAME
from EMPLOYEES inner join yourList using(EMPLOYEE_ID)
order by position;

如果您想在列表更改时限制要编写的代码，您可以通过拆分字符串来构建您的列表：

with yourList(EMPLOYEE_ID, position) as (
    SELECT regexp_substr(stringList, '[^,]+', 1, level), level
      FROM (select '151,149,145,147,155' as stringList from dual)
      CONNECT BY instr(stringList, ',', 1, level - 1) > 0
)
select EMPLOYEE_ID, FIRST_NAME
from EMPLOYEES inner join yourList using(EMPLOYEE_ID)
order by position;

通过这种方式，您只需编辑您的 ID 列表，无需对您的查询进行其他修改。

【讨论】：