Postgres：无法识别未知类型的排序运算符

Question

我有这个带有准备语句的查询：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY 
LIMIT

我将 name ASC 的值发送到 </code> 并将 <code>10 的值发送到 </code></p> <p>出于某种原因，我收到此错误：</p> <pre><code>could not identify an ordering operator for type unknown

如果我硬编码 name ASC 而不是 $1，像这样：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY name ASC
LIMIT

它工作正常。

我做错了什么？

Answer 1

您不能将列名作为变量传递（除非您正在使用动态查询构建）

Answer 2

对于一列，您可以使用 CASE WHEN 对其进行参数化：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY 
  CASE WHEN  = 'name' THEN name
       WHEN  = 'col_name' THEN col_name
       ELSE ...
  END
LIMIT ;

或：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY 
  CASE 
       WHEN 'name' THEN name
       WHEN 'col_name' THEN col_name
       ELSE column_name -- default sorting
  END
LIMIT ;

使用 CASE 您不需要将列转换为相同的数据类型以避免隐式转换错误。

编辑：

SELECT sub.*
FROM (
    SELECT * FROM ONLY service_services
    UNION ALL
    SELECT * FROM fleet.service_services
    WHERE deleted=false
) As sub
ORDER BY 
    CASE 
           WHEN 'name' THEN name
           WHEN 'col_name' THEN col_name
           ELSE column_name -- default sorting
    END
LIMIT ;

Postgres：无法识别未知类型的排序运算符

Postgres: Could not identify an ordering operator for type unknown

sql

postgresql

prepared-statement