<category>

<Computer id="" layer="1" level="1" name="computer">

<Bijiben id="" layer="11" level="2" name="bijiben">

<Hp id="" layer="111" level="3" name="HP">

....

</Hp>

<Gateway id="" s="112" level="3" name="Gateway">

...

</Gateway>

......

</Bijiben>

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<Taishiji id="" level="12" layer="2" name="taishiji">

<Dell id="" level="121" name="Dell">

...

</Dell>

<Lenover id="" level="122" name="lenover">

...

</Lenover>

</Taishiji>

</Computer>

<Home id="" level="2" layer="1" name="home">

<Bed id="" level="21" layer="2" name="bed">

<Baolong id="" level="211" name="baolong">

</Baolong>

<Wanbao id="" level="212" name="wanbo">

</Wanbao>

</Bed>

<Dianshi id="" level="22" layer="2" name="dianshiji">

<Changhong id="" level="221" name="changhong">

</Changhong>

<TCL id="" level="222" name="tcl">

</TCL>

</Dianshi>

</Home>

</category>

create table categorys(

id int auto_increment primary key,

name varchar(50),

layer varchar(20) not null,

level varchar(20) not null

);

------------------------------------------------------------------------------------------------------------

select name,layer,level from categorys where layer like '2%' && level='2' && layer!='2';

------------------------------------------------------------------------------------------------------------

--N：表示第几层，层级；

-----------------------------------------------------------------------------------------------------

select name from categorys where layer like '1%' && level='N' && layer!='N';

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