如何编写SQL查询实现表T1中Addr匹配Code的两行数据合并需求

实现逻辑为对表T1做自连接，将主表的Addr字段和关联表的Code字段做等值匹配，即可输出符合要求的合并结果：

SELECT 
  t1_1.CID,
  t1_1.Code,
  t1_1.Addr,
  t1_1.City,
  t1_1.State,
  t1_2.City,
  t1_2.State
FROM T1 t1_1
INNER JOIN T1 t1_2
ON t1_1.Addr = t1_2.Code

注意：部分数据库不允许查询结果存在同名字段，你可以给重复的City和State字段自定义别名区分，示例：

SELECT 
  t1_1.CID,
  t1_1.Code,
  t1_1.Addr,
  t1_1.City AS source_city,
  t1_1.State AS source_state,
  t1_2.City AS match_city,
  t1_2.State AS match_state
FROM T1 t1_1
INNER JOIN T1 t1_2
ON t1_1.Addr = t1_2.Code

执行上述语句后，输出结果和你给出的样例完全一致。

内容的提问来源于stack exchange，提问作者Sandhya Koduru