mysql遞迴查詢，查詢子集合，查詢父集合

--drop function `getchildlist`  

create function `getchildlist`(rootid varchar(100)) 
returns longtext 
begin 
declare str longtext;
declare cid longtext; 
set str = '$'; 
set cid = rootid; 
while cid is not null do 
set str = concat(str, ',', cid); 
select group_concat(id) into cid from treenodes where find_in_set(parentid, cid) > 0; 
end while; 
return str; 
end

select getchildlist('447');

select * from tbl_institution where find_in_set(id,getchildlist(200));

--drop function `getparentlist`  

create function `getparentlist`(rootid varchar(100)) 
returns varchar(1000) 
begin 
declare fid varchar(100) default ''; 
declare str varchar(1000) default rootid; 
while rootid is not null do 
set fid =(select parentid from treenodes where id = rootid); 
if fid is not null then 
set str = concat(str, ',', fid); 
set rootid = fid; 
else 
set rootid = fid; 
end if; 
end while; 
return str; 
end

select getparentlist('1088'); 

select * from tbl_institution where find_in_set(id,getparentlist(200));

關於longtext的說明

在我實際使用過程中，varchar已經不滿足我所處理的資料長度，所以在此使用了longtext，最大長度為4 294 967 295個字元

關於使用group_concat字串過長被擷取的問題

修改配置檔案：my.ini

在[mysqld]下新增配置：group_concat_max_len = 102400

參考文章

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