如何在检索结果里面增加一个表中没有的列?

Question

c 根据什么得到呢
test
---
select a,b,1 as c
from test

Answer 1

SQL> select * from test_tab;COL_A      COL_B
---------- ----------
C1         C2
V1         aa
V1         bb
V1         cc
V1         dd
V2         kk
V2         qq7 rows selectedSQL> select a.*,'x' col_c from test_tab a;COL_A      COL_B      COL_C
---------- ---------- -----
C1         C2         x
V1         aa         x
V1         bb         x
V1         cc         x
V1         dd         x
V2         kk         x
V2         qq         x7 rows selected