SQL 语句 如果数据库中没有该条记录则insert，如果有，则什么都不做

Question

如题，这个SQL语句该怎么写？谢谢

Answer 1

[code="sql"]
merge into table_a t
using (select 'xx' id, 'xxx' c1, 'xxxx' c2 from dual) x
on (t.id = x.id)
when not matched then
insert (id, c1, c2) values (x.id, x.c1, x.c2);

[/code]
Oracle 10 或以上可以只写when not matched或者when matched一种情况，9i需要when not matched和when matched写全。