防止一次写入多条相同数据

#Oracle
INSERT 
WHEN (NOT EXISTS(SELECT 1 FROM APP_ID WHERE IDTYPE = '80'))
THEN INTO APP_ID(IDTYPE,id) 
SELECT '80','2' from dual
#注：SELECT '80','2' from dual此处可加别名，已保万无一失。
SELECT '80' a,'2' b from dual

#Mysql
INSERT INTO APP_ID(IDTYPE,id) SELECT 80,2 from dual
WHERE NOT EXISTS(SELECT 1 FROM APP_ID WHERE IDTYPE = 80)

满足条件才插入