Question

我想在现有表中添加一列，其值取决于另一列STORE。 STORE有两个值，T或D.如果存储值为T，那么我希望添加列中的值为1，否则为零。有什么办法吗？

Answer 1

虚拟列可以在11g中执行：

SQL> create table yourtab (store varchar2(1));

Table created.

SQL> alter table yourtab add col as (case store when 'T' then 1 else 0 end);

Table altered.

SQL> insert into yourtab (store) values ('T');

1 row created.

SQL> insert into yourtab (store) values ('D');

1 row created.

SQL> select * from yourtab;

S        COL
- ----------
T          1
D          0

或触发方式，如果你的10g或之前：

SQL> create table yourtab (store varchar2(1), col number);

Table created.

SQL> create trigger yourtab_biu
  2  before insert or update on yourtab
  3  for each row
  4  declare
  5  begin
  6    :new.col := case :new.store when 'T' then 1 else 0 end;
  7  end;
  8  /

Trigger created.

SQL> insert into yourtab (store) values ('T');

1 row created.

SQL> insert into yourtab (store) values ('D');

1 row created.

SQL> select * from yourtab;

S        COL
- ----------
T          1
D          0

Answer 2

Oracle不支持create或alter table命令。

相反，请使用：

ALTER TABLE your_table ADD c INTEGER;

UPDATE your_table SET c = CASE WHEN store = 'T' THEN 1 ELSE 0 END;

Answer 3

视图可以是一个解决方案：

create view v_your_table as
select  your_table.*, case when STORE = 'T' than 0 else 1 end as comp from your_table;

向现有表添加一列，其值取决于其他列

3 个答案: