查询的问题按案例选择不同的顺序

Question

在问题的帮助下，我学会了如何使用SELECT DISTINCT 和ORDER BY：
How to use DISTINCT and ORDER BY in same SELECT statement?

我从这个问题中学会了使用ORDER BY CASE：
How do I return rows with a specific value first?

但是我有一个很难写的查询：

我有一张表CUSTOMER 和一列NAME，我想获取所有不同 客户的姓名，我想先找到名称“Hamza”。

SELECT DISTINCT "CUSTOMER"."NAME",
    Max("CUSTOMER"."NAME")
FROM "CUSTOMER"
WHERE
    "CUSTOMER".id >= 2
GROUP BY "CUSTOMER"."NAME"
ORDER BY CASE WHEN ("CUSTOMER"."NAME" = 'HAMZA' ) THEN 1 ELSE 2 END

错误：

错误：对于 SELECT DISTINCT，ORDER BY 表达式必须出现在选择列表中
第 15 行：按大小写排序 WHEN ("CUSTOMER"."NAME" = 'HAMZA') THEN 1 EL...
_________________.^
SQL 状态：42P10
字符：372

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编辑

解决方法：

SELECT "CUSTOMER"."NAME", -- distinct keyword removed here
    Max("CUSTOMER"."NAME")
FROM "CUSTOMER"
WHERE
    "CUSTOMER".id >= 2
GROUP BY "CUSTOMER"."NAME"
ORDER BY
CASE WHEN ("CUSTOMER"."NAME" = 'HAMZA' ) THEN 1 ELSE 2 END,
CASE WHEN ("CUSTOMER"."NAME" = 'GIORNO' ) THEN 1 ELSE 2 END

Answer 1

分组已经确保您获得不同的客户名称。只需删除此修饰符，您就可以了：

SELECT "CUSTOMER"."NAME", -- distinct keyword removed here
    Max("CUSTOMER"."NAME")
FROM "CUSTOMER"
WHERE
    "CUSTOMER".id >= 2
GROUP BY "CUSTOMER"."NAME"
ORDER BY CASE WHEN ("CUSTOMER"."NAME" = 'HAMZA' ) THEN 1 ELSE 2 END

Answer 2

我想获取客户的所有不同名称，并且我想首先找到名称“Hamza”。

为什么不这样做呢？

SELECT "CUSTOMER"."NAME"
FROM "CUSTOMER" 
GROUP BY "CUSTOMER"."NAME" 
ORDER BY ("CUSTOMER"."NAME"  = 'Hamza') DESC

将SELECT DISTINCT 与聚合函数一起使用通常只会混淆查询逻辑。

我也不知道你为什么要选择两次名字。