oracle 字符串拆分，序列，插入数据

 insert into stud_sname1_417
(id,sname1) select seq_sname1_417,distinct substr(name,1,1) from name;

请问为什么是 missing expression

insert into stud_sname1_417
(id,sname1)
SELECT distinct seq_sname1_417, substr(name,1,1) from name;

---distinct 放错位置了，要放在select 后面