树形式的MYSQL输出或添加级别(Parent-Child)
作者：互联网
以下是我在桌子上的内容.
为myTable
++++++++++++++++++++
Parent + Child
++++++++++++++++++++
C1 + G1
C1 + G2
C1 + G3
G3 + D1
G3 + D2
C1 + G4
G4 + D3
G4 + D4
C2 + G5
C2 + G6
C2 + G7
C2 + G8
++++++++++++++++++++
我想要的是如下使用MYSQL.
C1
G1
G2
G3
D1
D2
G4
D3
D4
C2
G5
G6
G7
G8
如果可以在MYSQL中使用,请告诉我.输出类似于TREE.
更新1
如果我得到像下面这样的新表也没关系,所以我可以使用this example.
++++++++++++++++++++++++++++++++++++++++
Parent + Child + PLevel + CLevel
++++++++++++++++++++++++++++++++++++++++
C1 + G1 + 1 + 2
C1 + G2 + 1 + 2
C1 + G3 + 1 + 2
G3 + D1 + 2 + 3
G3 + D2 + 2 + 3
C1 + G4 + 1 + 2
G4 + D3 + 2 + 3
G4 + D4 + 2 + 3
C2 + G5 + 1 + 2
C2 + G6 + 1 + 2
C2 + G7 + 1 + 2
C2 + G8 + 1 + 2
++++++++++++++++++++++++++++++++++++++++
注意：我已经开始使用1级别(例如,我的级别从0开始).如果我得到这个从0开始的新表也没关系.
解决方法:
虽然您不能使用单个查询,但您可以使用存储过程…唯一的预先要求,您需要在现有样本表中添加2个以上的记录来表示“C1”和“C2”ARE顶级…添加“父”字段为空的记录,子级别为“C1”,另一个为“C2”.这将“准备”最顶层的父级.对于后续层次结构关联,否则您没有顶层层次结构的起始“基础”.它还需要一个“主键”列(我在这个脚本中创建的“IDMyTable”只是1-x顺序,但假设你的表上有一个自动增量列来代替).
我已经包含了所有输出列以显示它是如何构建的,但是这个例程的前提是基于预期的列输出创建一个表,还有额外的用于在构建时保持下游的层次表示.为了确保它们保持正确的方向,因为层越来越深,我正在整理“ID”列 – 你会看到它在最终结果集中是如何工作的.
然后,在最终结果集中,我根据层次结构数据的深度预填充空间.
循环将根据在前面的结果集中找到的父项添加任何记录,但仅在尚未添加ID时(防止重复)…
要查看循环顺序是如何不断附加的,您可以运行最后一个查询而不用顺序,并查看每个迭代如何合格并添加先前的层次结构级别…
-- --------------------------------------------------------------------------------
-- Routine DDL
-- Note: comments before and after the routine body will not be stored by the server
-- --------------------------------------------------------------------------------
DELIMITER $$
CREATE DEFINER=`root`@`localhost` PROCEDURE `GetHierarchy2`()
BEGIN
-- prepare a hierarchy level variable
set @hierlvl := 00000;
-- prepare a variable for total rows so we know when no more rows found
set @lastRowCount := 0;
-- pre-drop temp table
drop table if exists MyHierarchy;
-- now, create it as the first level you want...
-- ie: a specific top level of all "no parent" entries
-- or parameterize the function and ask for a specific "ID".
-- add extra column as flag for next set of ID's to load into this.
create table MyHierarchy as
select
t1.IDMyTable,
t1.Child AS Parent,
@hierlvl as IDHierLevel,
cast( t1.IDMyTable as char(100)) FullHierarchy
from
MyTable t1
where
t1.Parent is null
OR t1.Parent = '';
-- how many rows are we starting with at this tier level
set @lastRowCount := ROW_COUNT();
-- we need to have a "primary key", otherwise our UPDATE
-- statement will nag about an unsafe update command
alter table MyHierarchy add primary key (IDMyTable);
-- NOW, keep cycling through until we get no more records
while @lastRowCount > 0 do
-- NOW, load in all entries found from full-set NOT already processed
insert into MyHierarchy
select
t1.IDMyTable,
t1.Child as Parent,
h1.IDHierLevel +1 as IDHierLevel,
concat_ws( ',', h1.FullHierarchy, t1.IDMyTable ) as FullHierarchy
from
MyTable t1
join MyHierarchy h1
on t1.Parent = h1.Parent
left join
MyHierarchy h2
on t1.IDMyTable = h2.IDMyTable
where
h2.IDMyTable is null;
set @lastRowCount := row_count();
-- now, update the hierarchy level
set @hierLevel := @hierLevel +1;
end while;
-- return the final set now
select
*, concat( lpad( ' ', 1 + (IDHierLevel * 3 ), ' ' ), Parent ) as ShowHierarchy
from MyHierarchy
order by FullHierarchy;
END
标签：sql,mysql,format,tree,parent-child 来源： https://codeday.me/bug/20191002/1841276.html