Sql Postgres:无法识别未知类型的排序运算符

我对准备好的声明提出了这个问题：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY $1
LIMIT $2

我将

name ASC

的值发送到

$1

和

10

到

$2

出于某种原因，我会出现以下错误：

could not identify an ordering operator for type unknown

如果我硬编码

名称ASC

而不是$1，如下所示：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY name ASC
LIMIT $1

它工作得很好

---

我做错了什么？

您不能将列名作为变量传递（除非您使用的是动态查询构建）

对于一列，您可以在参数化时使用

大小写：

SELECT * FROM ONLY service_services
UNION ALL
SELECT * FROM fleet.service_services
WHERE deleted=false
ORDER BY 
  CASE WHEN $1 = 'name' THEN name
       WHEN $1 = 'col_name' THEN col_name
       ELSE ...
  END
LIMIT $2;

或：

使用
CASE
您可能需要将列强制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 $1
           WHEN 'name' THEN name
           WHEN 'col_name' THEN col_name
           ELSE column_name -- default sorting
    END
LIMIT $2;

谢谢，但是它说，
无效的UNION/INTERSECT/EXCEPT ORDER BY子句（@JahongirRahmonov）只尝试一个查询，而不使用UNION@JahongirRahmonov尝试使用子查询
SELECT sub.*
FROM (
    SELECT * FROM ONLY service_services
    UNION ALL
    SELECT * FROM fleet.service_services
    WHERE deleted=false
) As sub
ORDER BY 
    CASE $1
           WHEN 'name' THEN name
           WHEN 'col_name' THEN col_name
           ELSE column_name -- default sorting
    END
LIMIT $2;