Question

基本上我想根据他们出现的其他表格对我的客户进行分类。我怀疑这种语法是远程正确的，但希望这个要点可以通过：

SELECT customer_id,
CASE customer_id
WHEN [customer_id is in tableA] THEN 'customer_segment_1'
WHEN [customer_id is in tableB] THEN 'customer_segment_2'
ELSE 'customer_segment_3' END
AS 'customer_segment'
FROM customers

Answer 1

确定＆＃34; customer_id是否在tableA＆＃34;您只需要加入该表格，使用left outer来计算tableA中不的ID：

SELECT tableC.customer_id,
       CASE  
          WHEN tableA.customer_id is not null THEN 'customer_segment_1'
          WHEN tableB.customer_id is not null THEN 'customer_segment_2'
    ELSE 'customer_segment_3' END
    AS customer_segment
 FROM tableC
 LEFT OUTER JOIN tableA on tableC.customer_id = tableA.customer_id     
 LEFT OUTER JOIN tableB on tableC.customer_id = tableB.customer_id

Answer 2

类似的东西：

SELECT tableC.customer_id,
CASE WHEN tableA.customer_id IS NOT NULL THEN 'SegmentA' 
   WHEN tableB.customer_id IS NOT NULL THEN 'SegmentB' ELSE 'SegmentC' END CASE AS Segment
FROM tableC LEFT JOIN tableA ON tableC.customer_id=tableA.customer_id
    LEFT JOIN tableB ON tableC.customer_id=tableB.customer_id

MySQL：根据其他表的内容创建新列

2 个答案: