sql - 在 SNOWFLAKE SQL 中选择和聚合不同 id 的变量

Question

我有 SNOWFLAKE 数据库表，其中包含客户及其交易类型:

customer_id type
1   a
1   a
2   b
2   b
2   b
3   a
3   b
3   a

在输出时，我需要不同的客户 ID 和交易类型:

customer_id type
1   a
2   b
3   mixed

我的代码不起作用:

SELECT 
"customer_id",
CASE WHEN type = 'a' THEN "a" 
WHEN type = 'b' THEN "b"
ELSE "mixed" END OVER (PARTITION BY "customer_id" )  AS "type"
FROM CUSTOMERS

Answer 1

您需要聚合和一个 CASE 表达式来检查每个 customer_id 的不同 type 数量:

SELECT customer_id,
       CASE WHEN COUNT(DISTINCT type) = 1 THEN MAX(type) ELSE 'mixed' END AS type
FROM CUSTOMERS
GROUP BY customer_id;

编写 CASE 表达式的另一种方法是:

CASE WHEN MIN(type) = MAX(type) THEN MAX(type) ELSE 'mixed' END AS type

我假设 type 不可为空。