附件：city.sql - djmg
mysql查詢某節點下層的所有元素節點：
select parentid, areaid, areacode,areaname, level, center
from city_area
where find_in_set(areaid,
(select group_concat(childrenids) from (
select (
select @childrenids:=group_concat(areaid) from city_area where find_in_set(parentid, @childrenids)) as childrenids
-- ,ceiling( length(@childrenids) / 5 )
from (select @childrenids:=?) var,city_area c where @childrenids is not null
) a )
--and areaname like '%區%';
mysql查詢某節點上層的所有元素節點：
select parentid, areaid, areacode,areaname, level, center
from city_area
where find_in_set(areaid,
(select group_concat(childrenids) from (
select (
select @childrenids:=group_concat(parentid) from city_area where find_in_set(areaid, @childrenids)) as childrenids
-- ,ceiling( length(@childrenids) / 5 )
from (select @childrenids:=?) var,city_area c where @childrenids is not null
) a )
--and areaname like '%區%';
兩個查詢的不同點在於最內層的查詢將父子id位置對換了一下
(select @childrenids:=group_concat(parentid) from city_area where find_in_set(areaid, @childrenids)) as childrenids
(select @childrenids:=group_concat(areaid) from city_area where find_in_set(parentid, @childrenids)) as childrenids
問題:group_concat函式被截斷的問題
mysql的 group_concat 函式預設返回1024個位元組長度，超過長度的會被截斷;
命令列下輸入：
set global group_concat_max_len=1024000;
or set session group_concat_max_len=1024000;
jpa原生sql':'轉義問題
字元:在jpa原生sql會被看作是變數的字首
@childrenids:=? ==> @childrenids\\:=?
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