使用 CASE 表达式更新列抛出错误：列“external_uuid”是 uuid 类型，但表达式是布尔类型

Question

我有一个表，我想在其中更新列 external_uuid，前提是该列已经没有值：

private const val updateSql = """
  update customer
  set
      external_id = :externalId,
      external_uuid = CASE when external_uuid is null then external_uuid = :externalUuid END,
      name = :name,
      address = :address,
      zip_code = :zipCode,
      zip_area = :zipArea,
      country_code = :countryCode,
      is_deleted = :markedForRemoval
  where is_deleted = false AND (external_uuid = :externalUuid OR (external_id = :externalId AND external_subcustomer = :subCustomer))
"""

但是，如果我进行这样的更新，我会收到错误：

 ERROR: column "external_uuid" is of type uuid but expression is of type boolean

如何在更新时有条件地仅设置一列？

Answer 1

您的CASE 表达式返回此布尔表达式的结果：

external_uuid = :externalUuid

可能是true 或false，不能存储在定义为uuid 的列中，这就是您收到错误的原因。

你应该这样写：

external_uuid = CASE when external_uuid is null then :externalUuid else external_uuid END

或：

external_uuid = coalesce(external_uuid, :externalUuid)