left join问题

Question

表A记录如下：
aID                    aNum
1|ww                   a20050111
2|fefw                  a20050112
3|fwea                  a20050113
4|fwaef                 a20050114
5|fewaff                a20050115
表B记录如下:
bID                      bName
1|fewafawe               2006032401
2|fwaf                   2006032402
3|fwaef                  2006032403
4|fwa                    2006032404
8|fewfwef                2006032408
怎么写才能输出  select * from A left join B on A.aID = B.bID；    这样写 没用啊 mysql有包含某个字符串的函数么
结果如下:
aID               aNum                          bID                  bName
1                   a20050111                1                      2006032401
2                   a20050112                2                     2006032402
3                   a20050113                3                     2006032403
4                   a20050114                4                     2006032404
5                   a20050115                NULL              NULL

Answer 1

select * from A left join B on left(A.aID,1) = left(B.bID,1)

Answer 2

select left(A.aID,1),a.num,left(B.bID,1),b.name from A left join B on left(A.aID,1) = left(B.bID,1)

Answer 3

or
select left(A.aID,instr(a.aid,'|')-1),a.num,left(B.bID,instr(b.bid,'|')-1),b.name from A left join B on 
left(A.aID,instr(a.aid,'|')-1)=left(b.bID,instr(b.bid,'|')-1)

Answer 4

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