sql字符串问题

求一条语句：若name前五个字符相同，只取val最小的一条

name    val
aaaaabb  11
aaaaacc  12
AAAAABB  10
AAAAACC  9

返回
name    val
aaaaabb  11
AAAAACC  9

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SQL code:
select name,min(val) from Table group by left(name,5)

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表中字段不只含有name 和 val，还有很多别的字段。用group by 不行吧

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SQL code:
select * from Table t where not exists (select 1 from table where t.name=name,t.val>val)

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若
name val
aab 12
aab 13

则返回
name val
aab  12

意思是字符长度不超过5的时候也要包括在内

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SQL code:
select * from tb t where not exists(select 1 from tb where name=t.name and val<t.val)

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SELECT * from TB T WHERE VAL=SELECT (min(val) from TB left(name,5)=left(T.name,5))

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SQL code:
select * from Table t where not exists (select 1 from table where t.name=name and t.val>val