查询从SQL Server到SQLite的转换

Question

我需要在SQLite中存储一棵树。我发现了一个很不错的方法，用于SQL Server的位置：

Tree structures in ASP.NET and SQL Server

与触发器的概念是明确的结束前瞻性的思维。

我试图描述的触发器转换为SQLite的

SQL Server版本：

CREATE TRIGGER dfTree_UpdateTrigger 
ON dfTree 
FOR UPDATE AS 
-- if we've modified the parentId, then we 
-- need to do some calculations 
IF UPDATE (parentId) 
UPDATE child 
-- to calculate the correct depth of a node, remember that 
--  - old.depth is the depth of its old parent 
--  - child.depth is the original depth of the node 
--   we're looking at before a parent node moved. 
--   note that this is not necessarily old.depth + 1, 
--   as we are looking at all depths below the modified 
--   node 
-- the depth of the node relative to the old parent is 
-- (child.depth - old.depth), then we simply add this to the 
-- depth of the new parent, plus one. 
    SET depth = child.depth - old.depth + ISNULL(parent.depth + 1,0), 
    lineage = ISNULL(parent.lineage,'/') + LTrim(Str(old.id)) + '/' + 
        right(child.lineage, len(child.lineage) -  len(old.lineage)) 
-- if the parentId has been changed for some row 
-- in the "inserted" table, we need to update the 
-- fields in all children of that node, and the 
-- node itself     
FROM dfTree child 
INNER JOIN inserted old ON child.lineage LIKE old.lineage + '%' 
-- as with the insert trigger, attempt to find the parent 
-- of the updated row 
LEFT OUTER JOIN dfTree parent ON old.parentId=parent.id 

我的SQLite版本到现在为止：

CREATE TRIGGER IF NOT EXISTS sc_compare_UpdateTrigger 
AFTER UPDATE ON dfTree 
FOR EACH ROW 
BEGIN 
    UPDATE child 
     SET depth = child.depth - OLD.depth + IFNULL(parent.depth + 1,0), 
     lineage = IFNULL(parent.lineage,'/') + LTrim(CAST(OLD.id AS TEXT)) +  '/' + 
      right(child.lineage, len(child.lineage) - len(OLD.lineage)) 
    FROM dfTree child 
    INNER JOIN inserted OLD ON child.lineage LIKE OLD.lineage + '%' 
    LEFT OUTER JOIN dfTree parent ON OLD.parentId=parent.id 
END; 

对于此版本，一个“错误：近“FROM”：语法错误“occours。

我在正确的轨道上？ 是否可以使用SQLite构建此触发器功能？

Answer 1

Sqlite UPDATE语法不支持FROM子句。 还请注意表中只有NEW,OLD行中的FOR EACH ROW触发器。