Sql 列中的源名称

我正在尝试从查询中编写一个源表，如

coalesce(t1.id, t2.id) as id,
 ??? as source_table 
from t1
left join t2 on t1.id = t2.id

---

Postgres中是否存在我可以在源表字段中插入的函数？

我认为您必须使用

CASE

语句：

SELECT
  COALESCE(t1.id,t2.id) as id,
  CASE WHEN t1.id IS NULL THEN 't2' ELSE 't1' END as source_table,
FROM
  t1 LEFT JOIN t2 ON t1.id = t2.id;