理解 with递归调用 Sqlserver 树查询

--with用法
--可以这么理解

with SQL语句变量或者叫临时表名 as(
    SQL语句
)
select * from SQL语句变量或者叫临时表名

--递归调用
with CTE as(
    select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
    union all
    select a.ZTBM_ID,a.ztbm_name,a.ParentId from TB_ZYM_ZTBM a inner join CTE on a.ParentId=CTE.ZTBM_ID
)
select * from CTE
--此语句可以理解如下

--同上一个语句
    --最顶层 1
    select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
    union all
    select a.ZTBM_ID,a.ztbm_name,a.ParentId from TB_ZYM_ZTBM a 
    inner join --此处括弧可以理解为最顶层的CTE   此处红色CTE即上一个SQL语句的CTE
    (
        --第二层
        select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
        union all
        select a.ZTBM_ID,a.ztbm_name,a.ParentId from TB_ZYM_ZTBM a 
        inner join --此处括弧可以理解为第二层的CTE
        (
            --第三层
            select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
            union all
            select a.ZTBM_ID,a.ztbm_name,a.ParentId from TB_ZYM_ZTBM a 
            inner join 
            (
                --第四层
                select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
                union all
                select a.ZTBM_ID,a.ztbm_name,a.ParentId from TB_ZYM_ZTBM a 
                inner join 
                (
                    select ZTBM_ID,ztbm_name,ParentId from TB_ZYM_ZTBM where ParentId is null or ParentId=‘‘
                    --inner join....    层层嵌套
                    --最底层
                )
                CTE on a.ParentId=CTE.ZTBM_ID
            )
            CTE on a.ParentId=CTE.ZTBM_ID
            
            
        )
        CTE on a.ParentId=CTE.ZTBM_ID
    )
    CTE on a.ParentId=CTE.ZTBM_ID

with CTE as    
(     
-->Begin 一个定位点成员     
 select ZTBM_ID, ztbm_name,ParentId,cast(ztbm_name as nvarchar(max)) as TE,  
        ROW_NUMBER()over(order by getdate()) as OrderID,0 as Levle  
        from TB_ZYM_ZTBM where  deleteMark=1 and (ParentId is null or ParentId=‘‘) 
-->End      
union all     
-->Begin一个递归成员     
 select TB_ZYM_ZTBM.ZTBM_ID, TB_ZYM_ZTBM.ztbm_name,TB_ZYM_ZTBM.ParentId,cast(replicate(‘　　‘,Levle+1)+‘|_‘+TB_ZYM_ZTBM.ztbm_name as nvarchar(MAX)) as TE,  
        CTE.OrderID*100+ROW_NUMBER()over(Order by GETDATE()) as OrderID  ,Levle+1 as Levle
        from TB_ZYM_ZTBM inner join CTE     
        on TB_ZYM_ZTBM.ParentId=CTE.ZTBM_ID     
-->End     
)     
select * from CTE  
order by LTRIM(OrderID)