sql - MS SQL 临时表循环

Question

需要有关 sql 循环查询的帮助

我的 table :

我的预期输出:

我只能得到 1 行..

 declare @ID nvarchar(50) = (select EMP_ID from HRS_WORKFLOW01);


    CREATE TABLE #TEMP(EMP_ID NVARCHAR(200),EMP_L1 NVARCHAR(200),EMP_L2 NVARCHAR(200),EMP_L3 NVARCHAR(200),EMP_L4 NVARCHAR(200))
    DECLARE @L1 NVARCHAR(50);
    DECLARE @L2 NVARCHAR(50);
    DECLARE @L3 NVARCHAR(50);
    DECLARE @L4 NVARCHAR(50);

    SET @L1 = (SELECT L1EmplNo FROM HRS_WORKFLOW01 WHERE EMP_ID =@ID)
    INSERT INTO #TEMP (EMP_ID,EMP_L1)VALUES(@ID,@L1)

    SET @L2 = (SELECT L1EmplNo FROM HRS_WORKFLOW01 WHERE EMP_ID =@L1)
    UPDATE #TEMP SET EMP_L2=@L2 WHERE EMP_ID=@ID

    SET @L3 = (SELECT L1EmplNo FROM HRS_WORKFLOW01 WHERE EMP_ID =@L2)
    UPDATE #TEMP SET EMP_L3=@L3 WHERE EMP_ID=@ID

    SET @L4 = (SELECT L1EmplNo FROM HRS_WORKFLOW01 WHERE EMP_ID =@L3)
    UPDATE #TEMP SET EMP_L4=@L4 WHERE EMP_ID=@ID

    SELECT * FROM #TEMP

Answer 1

您需要使用递归CTE

;WITH DATA
     AS (SELECT *
         FROM   (VALUES ('ALI','ABU'),
                        ('JOSH','LIM'),
                        ('JAMES','KAREN'),
                        ('LIM','JERRY'),
                        ('JERRY','GEM')) TC(EMP_ID, EMP_L1)),
     REC_CTE
     AS (SELECT EMP_ID,
                EMP_L1,
                Cast(EMP_L1 AS VARCHAR(8000)) AS PARENT,
                LEVEL = 1
         FROM   DATA
         UNION ALL
         SELECT D.EMP_ID,
                D.EMP_L1,
                Cast(RC.PARENT + '.' + D.EMP_L1 AS VARCHAR(8000)),
                LEVEL = LEVEL + 1
         FROM   DATA D
                JOIN REC_CTE RC
                  ON RC.EMP_ID = D.EMP_L1)
SELECT TOP 1 WITH TIES EMP_ID,
                       EMP_L1 = COALESCE(Parsename(PARENT, 1), ''),
                       EMP_L2 = COALESCE(Parsename(PARENT, 2), ''),
                       EMP_L3 = COALESCE(Parsename(PARENT, 3), ''),
                       EMP_L4 = COALESCE(Parsename(PARENT, 4), '')
FROM   REC_CTE
ORDER  BY Row_number()OVER(PARTITION BY EMP_ID ORDER BY LEVEL DESC) 
OPTION (MAXRECURSION 0)

结果:

╔════════╦════════╦════════╦════════╦════════╗
║ EMP_ID ║ EMP_L1 ║ EMP_L2 ║ EMP_L3 ║ EMP_L4 ║
╠════════╬════════╬════════╬════════╬════════╣
║ ALI    ║ ABU    ║        ║        ║        ║
║ JAMES  ║ KAREN  ║        ║        ║        ║
║ JERRY  ║ GEM    ║        ║        ║        ║
║ JOSH   ║ LIM    ║ JERRY  ║ GEM    ║        ║
║ LIM    ║ JERRY  ║ GEM    ║        ║        ║
╚════════╩════════╩════════╩════════╩════════╝

注意:这认为最多可以有 4 个级别。为了将数据拆分为不同的列，我使用了 PARSENAME 函数，如果级别超过 4 个，该函数将不起作用。

如果您不想将父级拆分为不同的列，请删除 PARSENAME 并单独选择 PARENT 列。