不带LOOP的SQL中带有连接语句的动态查询

Question

我有以下元数据，它提供有关数据库中表层次结构的信息：

通过循环，我可以构造以下sql语句。还有另一种无需循环的整洁方法吗？

SELECT
  SubClassCode,
  ClassCode,
  DeptCode,
  DivisionCode INTO tempTable
FROM tblSBDivisionMaster T1
JOIN tblSBDepartmentMaster T2
  ON T2.ParentID = T1.DivisionID
JOIN tblSBClassMaster T3
  ON T3.ParentID = T2.DeptID
JOIN tblSBSubClassMaster T4
  ON T4.ParentID = T3.ClassID

带有循环示例：

declare @merchandiseHierCount as int ,@nextrowscount as int,@join as varchar(1000),@firstTable as varchar(200),@codeColumns as varchar(1000)

 SELECT
     @codeColumns = COALESCE(@codeColumns + ',', '') + MasterCodeColumn
 FROM  tblsbhierarchy
     WHERE HierarchyType = 1
 ORDER BY HierLevel;





 SET @merchandiseHierCount = (SELECT
         COUNT(*)
     FROM tblsbhierarchy
     WHERE HierarchyType = 1)
select @firstTable = MasterTableName  FROM tblsbhierarchy
     WHERE HierarchyType = 1 and HierLevel =1
set @nextrowscount =1
 WHILE (@nextrowscount <= @merchandiseHierCount)
 begin
  declare @tableName as varchar(100),@heir as varchar(20),@IdColumn as varchar(100)

  select @tableName = MasterTableName,@heir= HierLevel,@IdColumn = MasterKeyColumn from tblsbhierarchy where HierLevel = @nextrowscount and HierarchyType=1
  if @nextrowscount >1
  begin
  SET @join = (SELECT
          CONCAT(@join,' join ' + @tableName + ' T' + @heir + ' on '
          +' T'+ @heir + '.' + @IdColumn + ' = T' + cast((@heir-1) as VARCHAR) + '.ParentId'))

           end
            set @nextrowscount = @nextrowscount+1
           end

 set  @join = 'Select '+ @codeColumns+  ' into temptable From ' + @firstTable +' T1 ' + @join

 select @join

最终查询，@ Squirrel对查询进行了一些修改。我请求的查询有一个小错误。所以我对最终结果做了更正。

declare @select nvarchar(max),
        @from   nvarchar(max),
        @sql    nvarchar(max)

;
WITH tbl
AS
(SELECT
HierLevel,MasterTableName,MasterKeyColumn,MasterCodeColumn
       ,tbl = 'T' + CONVERT(VARCHAR(5), HierLevel)
       ,parent = 'T' + CONVERT(VARCHAR(5), LAG(HierLevel) OVER (ORDER BY HierLevel))
       ,parentId = lag(MasterKeyColumn) over( ORDER by HierLevel)
    FROM tblsbhierarchy
    WHERE HierarchyType = 1)
SELECT
    @select = ISNULL(@select + ', ', 'SELECT ')
    + tbl + '.' + MasterCodeColumn
   ,@from = ISNULL(@from, '')
    +
    CASE
        WHEN HierLevel = 1 THEN 'INTO temptable' + CHAR(13)
        ELSE ''
    END
    +
    CASE
        WHEN HierLevel = 1 THEN 'FROM '
        ELSE 'JOIN '
    END
    + MasterTableName
    + ' AS ' + tbl + CHAR(13)
    +
    CASE
        WHEN HierLevel <> 1 THEN CHAR(9) + 'ON ' + tbl + '.ParentId' +  ' = ' + parent + '.'+parentId + CHAR(13)
        ELSE ''
    END
FROM tbl
ORDER BY HierLevel

SELECT
    @sql = @select + CHAR(13) + @from
 print  @sql

Answer 1

这将为您提供格式精美的查询。基本上，它使用字符串连接并检查HierLevel。如果level = 1或其他，则采取相应措施。 char(13)是回车符，因此当您执行PRINT时，会得到一个格式良好的可读查询

declare @select nvarchar(max),
        @from   nvarchar(max),
        @sql    nvarchar(max)

 ; with tbl as
 (
    select  *, 
            tbl = 'T' + convert(varchar(5), HierLevel), 
            parent  = 'T' + convert(varchar(5), LAG(HierLevel) OVER(ORDER BY HierLevel))
     from   tblsbhierarchy
    where   HierarchyType   = 1
 )
 select @select = isnull(@select + ', ', 'SELECT ')
                + tbl + '.' + MasterCodeColumn,
        @from   = isnull(@from, '')
                + case when HierLevel = 1 then 'INTO temptable' + char(13) else '' end
                + case when HierLevel = 1 then 'FROM ' else 'JOIN ' end
                + MasterTableName
                + ' AS ' + tbl + char(13)
                + case  when HierLevel <> 1
                        then char(9) + 'ON ' + tbl + '.' + MasterKeyColumn + ' = ' + parent + '.ParentId'  + char(13)
                        else ''
                        end
 from   tbl
 order by HierLevel

 select @sql    = @select + char(13) + @from
 print  @sql

/* RESULT
SELECT T1.DivisionCode, T2.DeptCode, T3.ClassCode, T4.SubClassCode
INTO temptable
FROM tblSBDivisionMaster AS T1
JOIN tblSBDepartmentMaster AS T2
    ON T2.DeptID = T1.ParentId
JOIN tblSBClassMaster AS T3
    ON T3.ClassID = T2.ParentId
JOIN tblSBSubClassMaster AS T4
    ON T4.SubClassID = T3.ParentId
*/