select t.* from tbuser t where substr(t.name,0,3) like 'aa%';

WITH t AS (
SELECT 1 ID,'aa11' NAME,'t1' INFO FROM dual
UNION ALL 
SELECT 2,'aa22', 't1' FROM dual
UNION ALL
SELECT 3, 'bb33', 't2' FROM dual
UNION ALL
SELECT 4, 'bb44', 't2' FROM dual
UNION ALL
SELECT 5, 'cc55', 't3'  FROM dual
UNION ALL
SELECT 6, 'cc66', 't3'  FROM dual
UNION ALL
SELECT 7, 'cs2', 'b'  FROM dual
UNION ALL
SELECT 8, 'ct5', 'b'  FROM dual
UNION ALL
SELECT 9, 'xw6', 'b'  FROM dual
UNION ALL
SELECT 10, '12sre', 'b'  FROM dual
)

SELECT * FROM t WHERE NAME LIKE 'aa%' OR NAME LIKE 'bb%' OR NAME LIKE 'cc%' ORDER BY id;

ID    NAME    INFO
1    aa11    t1
2    aa22    t1
3    bb33    t2
4    bb44    t2
5    cc55    t3
6    cc66    t3

------解决方案--------------------
SQL code

select t.* 
from tbuser t 
where upper(substr(t.name,0,1))=upper(substr(t.name,1,2));