mysql 分组问题

[jm_tn]

有uuid,ID等字段，ID有12个字符，前6个为地址码,如何根据ID的前6个字符进行分组；
select count(uuid) from a1 group by ??????????

[TR@SOE]

不知道MySQL有没有substr函数？

[makui]

select count(uuid) from a1 group by substring(id,1,6)

[iasky]

可以使用MySQL的SUBSTR函数

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_substr

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SUBSTR(str,pos), SUBSTR(str FROM pos), SUBSTR(str,pos,len), SUBSTR(str FROM pos FOR len)

SUBSTR() is a synonym for SUBSTRING().
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SUBSTRING(str,pos), SUBSTRING(str FROM pos), SUBSTRING(str,pos,len), SUBSTRING(str FROM pos FOR len)