如何用这个在 SQLite 中编写 sql？

Question

    WITH cteCountDownlines AS
( --=== Count each occurrence of EmployeeID in the sort path
 SELECT EmployeeID = CAST(SUBSTRING(h.SortPath,t.N,4) AS INT), 
        NodeCount  = COUNT(*) --Includes current node
   FROM dbo.Hierarchy h, 
        dbo.HTally t
  WHERE t.N BETWEEN 1 AND DATALENGTH(SortPath)
  GROUP BY SUBSTRING(h.SortPath,t.N,4)
) --=== Update the NodeCount and calculate the RightBower
 UPDATE h
    SET h.NodeCount  = downline.NodeCount,
        h.RightBower = (downline.NodeCount - 1) * 2 + LeftBower + 1
   FROM dbo.Hierarchy h
   JOIN cteCountDownlines downline
     ON h.EmployeeID = downline.EmployeeID
;

来自https://www.sqlservercentral.com/articles/hierarchies-on-steroids-1-convert-an-adjacency-list-to-nested-sets。 我尝试了很多方法，但没有奏效。 分开的 cteCountDownlines 和 join 工作得很好，但不知道如何结合它们

Answer 1

如果您使用的是 SQLite 3.33.0+，则可以使用 UPDATE...FROM 语法：

WITH cteCountDownlines AS (
 SELECT CAST(SUBSTR(h.SortPath,t.N,4) AS INT) EmployeeID, 
        COUNT(*) NodeCount
  FROM Hierarchy h INNER JOIN HTally t
  ON t.N BETWEEN 1 AND LENGTH(h.SortPath)
  GROUP BY SUBSTR(h.SortPath,t.N,4)
)
UPDATE Hierarchy AS h
SET NodeCount  = downline.NodeCount,
    RightBower = (downline.NodeCount - 1) * 2 + h.LeftBower + 1
FROM cteCountDownlines downline
WHERE h.EmployeeID = downline.EmployeeID;

对于 SQLite 3.15.0+，您可以使用以下语法：

WITH cteCountDownlines AS (
 SELECT CAST(SUBSTR(h.SortPath,t.N,4) AS INT) EmployeeID, 
        COUNT(*) NodeCount
  FROM Hierarchy h INNER JOIN HTally t
  ON t.N BETWEEN 1 AND LENGTH(h.SortPath)
  GROUP BY SUBSTR(h.SortPath,t.N,4)
)
UPDATE Hierarchy AS h
SET (NodeCount, RightBower) = (
  SELECT downline.NodeCount,
         (downline.NodeCount - 1) * 2 + h.LeftBower + 1
  FROM cteCountDownlines downline
  WHERE h.EmployeeID = downline.EmployeeID
);

请注意，没有等效于 SQL Server 的 DATALENGTH() 函数。
我使用的函数LENGTH()返回字符串中的字符数。