SQL Server 2017

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE [dbo].[BINSTOCK](
    ItemCode NVARCHAR(10) NOT NULL
    ,Quantity DECIMAL (19,6) NOT NULL
    ,WhsCode INT NOT NULL
    ,BinCode NVARCHAR (10) NOT NULL
    ,RunningTotalQty DECIMAL (19,6) NOT NULL
    );

INSERT INTO [dbo].[BINSTOCK]
    VALUES('A00001' , 7.000000, 98, '98-A001' , 7.000000),
    ('A00001' , 6.000000, 98, '98-A002' , 13.000000),
    ('A00001' , 12.000000, 98, '98-A003' , 25.000000),
    ('A00001' , 15.000000, 98, '98-A006' , 40.000000);

CREATE TABLE [dbo].[WOPICK](
    DocNum INT NOT NULL
    ,LineNum INT NOT NULL
    ,ItemCode NVARCHAR (10) NOT NULL
    ,Quantity DECIMAL (19,6) NOT NULL
    ,RunningTotalQty DECIMAL (19,6) NOT NULL
    );

INSERT INTO [dbo].[WOPICK]
    VALUES(901903,0,'A00001',12.000000, 12),
    (901904,0,'A00001',17.000000, 29);
    
SELECT * FROM BINSTOCK;
SELECT * FROM WOPICK;
    
WITH Bin AS (
  SELECT *, ROW_NUMBER() OVER(PARTITION BY ItemCode ORDER BY BinCode) AS BinRank
  FROM BINSTOCK
), Pick AS (
  SELECT *, ROW_NUMBER() OVER(PARTITION BY ItemCode ORDER BY DocNum) AS PickRank
  FROM WOPICK
), BinPick AS (
  SELECT
    b.ItemCode,
    b.Quantity AS BinQty,
    b.BinCode,
    b.BinRank,
    p.Quantity AS PickQty,
    p.DocNum,
    p.PickRank,
    CAST (
      CASE
        WHEN b.Quantity < p.Quantity
        THEN b.Quantity
        ELSE p.Quantity
        END
    AS DECIMAL) AS Picked,
    CAST (
      CASE
        WHEN b.Quantity < p.Quantity
        THEN p.Quantity - b.Quantity
        ELSE 0
        END
    AS DECIMAL) AS Required,
    CAST (
      CASE
        WHEN b.Quantity < p.Quantity
        THEN 0
        ELSE b.Quantity - p.Quantity
        END
    AS DECIMAL) AS Remaining,
    CAST (
      CASE
        WHEN b.Quantity < p.Quantity
        THEN null
        ELSE b.BinRank
        END
    AS NVARCHAR) AS LastFullBinRank
  FROM Bin b
  JOIN Pick p ON p.ItemCode = b.ItemCode
  WHERE b.BinRank = 1
  AND p.PickRank = 1
  UNION ALL
  SELECT
    ItemCode,
    BinQty,
    BinCode,
    BinRank,
    PickQty,
    DocNum,
    PickRank,
    CAST (
      CASE WHEN Remaining < Required
        THEN Remaining
        ELSE Required
        END
      AS DECIMAL) AS Picked,
    CAST (
      CASE WHEN Remaining < Required
        THEN Required - Remaining
        ELSE 0
        END
    AS DECIMAL) AS Required,
    CAST (
      CASE WHEN Remaining < Required
        THEN 0
        ELSE Remaining - Required
        END
    AS DECIMAL) AS Remaining,
    CAST (
      CASE WHEN Remaining < Required
        THEN null
        ELSE BinRank
        END
    AS NVARCHAR) AS LastFullBinRank
  FROM (
    SELECT
      b.ItemCode,
      b.Quantity AS BinQty,
      b.BinCode,
      b.BinRank,
      p.Quantity AS PickQty,
      p.DocNum,
      p.PickRank,
      bp.DocNum AS PrevDocNum,
      bp.Picked,
      bp.LastFullBinRank,
      CASE WHEN p.DocNum = bp.DocNum
        -- Same order.  Continue with required from previous.
        THEN bp.Required
        -- New order.  Required is new order quantity.
        ELSE p.Quantity
        END
      AS Required,
      CASE WHEN p.DocNum = bp.DocNum
        -- Same order.  Hence fresh bin.  Use quanity from this bin.
        THEN b.Quantity
        -- New order.  Hence used bin.  Use remaining carried over.
        ELSE bp.Remaining
        END
      AS Remaining
      FROM BinPick bp
      JOIN Pick p
        ON p.ItemCode = bp.ItemCode
        AND (
          -- Order complete.  Move to next order
          (bp.Required = 0 AND p.PickRank = bp.PickRank + 1)
          OR
          -- Order incomlete.  Continue with current Order
          (bp.Required > 0 AND p.PickRank = bp.PickRank)
        )
      JOIN Bin b
        ON b.ItemCode = bp.ItemCode
        AND (
          -- Order complete.  Resume at last full bin.
          (bp.Required = 0 AND b.BinRank = bp.LastFullBinRank)
          OR
          -- Order incomlete.  Move to next bin.
          (bp.Required > 0 AND bp.LastFullBinRank IS NULL AND b.BinRank = bp.BinRank + 1)
        )
  ) sub1
) SELECT * FROM BinPick

ItemCode	Quantity	WhsCode	BinCode	RunningTotalQty
A00001	7.000000	98	98-A001	7.000000
A00001	6.000000	98	98-A002	13.000000
A00001	12.000000	98	98-A003	25.000000
A00001	15.000000	98	98-A006	40.000000

DocNum	LineNum	ItemCode	Quantity	RunningTotalQty
901903	0	A00001	12.000000	12.000000
901904	0	A00001	17.000000	29.000000

ItemCode	BinQty	BinCode	BinRank	PickQty	DocNum	PickRank	Picked	Required	Remaining	LastFullBinRank
A00001	7.000000	98-A001	1	12.000000	901903	1	7	5	0	null
A00001	6.000000	98-A002	2	12.000000	901903	1	5	0	1	2
A00001	6.000000	98-A002	2	17.000000	901904	2	1	16	0	null
A00001	12.000000	98-A003	3	17.000000	901904	2	12	4	0	null
A00001	15.000000	98-A006	4	17.000000	901904	2	4	0	11	4