如何修复递归CTE查询中的“'ear'with'：语法错误”（flask / sqlalchemy）

Question

我正在尝试重现在SqlAlchemy
docs页面上找到的查询。在中设置完Part课程后models.py，这就是我所拥有的：

from app import app, db, models
from models import *

@app.route('/')
def test():
    included_parts = db.session.query(
                    Part.sub_part,
                    Part.part,
                    Part.quantity).\
                        filter(Part.part=="our part").\
                        cte(name="included_parts", recursive=True)

    incl_alias = db.aliased(included_parts, name="pr")
    parts_alias = db.aliased(Part, name="p")
    included_parts = included_parts.union_all(
        db.session.query(
            parts_alias.sub_part,
            parts_alias.part,
            parts_alias.quantity).\
                filter(parts_alias.part==incl_alias.c.sub_part)
        )

    q = db.session.query(
            included_parts.c.sub_part,
            db.func.sum(included_parts.c.quantity).
                label('total_quantity')
        ).\
        group_by(included_parts.c.sub_part).all()

    return 'test complete'

但这给出了一个错误：

OperationalError: (sqlite3.OperationalError) near "WITH": syntax error [SQL: u'WITH RECURSIVE included_parts(sub_part, part, quantity) AS \n(SELECT parts.sub_part AS sub_part, parts.part AS part, parts.quantity AS quantity \nFROM parts \nWHERE parts.part = ? UNION ALL SELECT p.sub_part AS p_sub_part, p.part AS p_part, p.quantity AS p_quantity \nFROM parts AS p, included_parts AS pr \nWHERE p.part = pr.sub_part)\n SELECT included_parts.sub_part AS included_parts_sub_part, sum(included_parts.quantity) AS total_quantity \nFROM included_parts GROUP BY included_parts.sub_part'] [parameters: ('our part',)]

生成的查询（从错误消息粘贴的副本）如下所示：

WITH RECURSIVE included_parts(sub_part, part, quantity) AS \n(SELECT parts.sub_part AS sub_part, parts.part AS part, parts.quantity AS quantity \nFROM parts \nWHERE parts.part = ? UNION ALL SELECT p.sub_part AS p_sub_part, p.part AS p_part, p.quantity AS p_quantity \nFROM parts AS p, included_parts AS pr \nWHERE p.part = pr.sub_part)\n SELECT included_parts.sub_part AS included_parts_sub_part, sum(included_parts.quantity) AS total_quantity \nFROM included_parts GROUP BY included_parts.sub_part

格式化（为了便于阅读，在不同位置使用换行符）：

WITH RECURSIVE included_parts(sub_part, part, quantity) AS (
    SELECT parts.sub_part AS sub_part, parts.part AS part, parts.quantity AS quantity 
    FROM parts
    WHERE parts.part = ? 
    UNION ALL 
    SELECT p.sub_part AS p_sub_part, p.part AS p_part, p.quantity AS p_quantity
    FROM parts AS p, included_parts AS pr 
    WHERE p.part = pr.sub_part
)
SELECT included_parts.sub_part AS included_parts_sub_part, sum(included_parts.quantity) AS total_quantity 
FROM included_parts 
GROUP BY included_parts.sub_part

并且，为了进行比较，这是sqlalchemy文档链接到的纯PostgreSQL查询：

WITH RECURSIVE included_parts(sub_part, part, quantity) AS (
    SELECT sub_part, part, quantity FROM parts WHERE part = 'our_product'
  UNION ALL
    SELECT p.sub_part, p.part, p.quantity
    FROM included_parts pr, parts p
    WHERE p.part = pr.sub_part
  )
SELECT sub_part, SUM(quantity) as total_quantity
FROM included_parts
GROUP BY sub_part

我可以看到的Postgre查询（我认为应该可以正常工作）与生成的唯一区别是：

1. 所有额外的“ AS”语句（SELECT parts.sub_part AS sub_partvs SELECT sub_part）
2. 不同的格式（生成的查询在奇怪的位置有换行符-例如，UNION ALL和之间没有换行符SELECT）

但是，据我所知，这两个都不应该导致语法错误…我也尝试过将Postgre查询作为原始SQL执行（尽管SQLAlchemy显然使用sqlite3，但仍然）：

    query = db.engine.execute(\
    '''WITH RECURSIVE included_parts(sub_part, part, quantity) AS (
SELECT sub_part, part, quantity FROM parts WHERE part = 'our_product'
UNION ALL
SELECT p.sub_part, p.part, p.quantity
FROM included_parts pr, parts p
WHERE p.part = pr.sub_part
)
SELECT sub_part, SUM(quantity) as total_quantity
FROM included_parts
GROUP BY sub_part''').all()

但是我仍然收到语法错误。

OperationalError: (sqlite3.OperationalError) near "WITH": syntax error [SQL: "WITH RECURSIVE included_parts(sub_part, part, quantity) AS (\nSELECT sub_part, part, quantity FROM parts WHERE part = 'our_product'\nUNION ALL\nSELECT p.sub_part, p.part, p.quantity\nFROM included_parts pr, parts p\nWHERE p.part = pr.sub_part\n)\nSELECT sub_part, SUM(quantity) as total_quantity\nFROM included_parts\nGROUP BY sub_part"]

我还尝试重新格式化生成的查询，并将其作为原始SQL执行，并获得相似的结果。

最后，我尝试在SQLite中编写查询并执行它：

WITH RECURSIVE included_parts(sub_part, part, quantity) AS (
    SELECT sub_part, part, quantity FROM parts WHERE part="our_product"
    UNION ALL
    SELECT parts.sub_part, parts.part, parts.quantity FROM parts, included_parts WHERE parts.part=included_parts.sub_part
)
SELECT sub_part, SUM(quantity) AS total_quantity
FROM included_parts
GROUP BY sub_part

这也会引发语法错误。

在这一点上，我不太确定该怎么做…看起来即使是WITH具有正确语法的查询仍然会引发错误。我知道根据文档和此处的（_http：//stackoverflow.com/a/24780445）答案，Sqlalchemy支持递归CTE查询。老实说，我不知道为什么所有这些查询都被认为语法错误。我的python代码实际上与docs中的示例相同。

我需要安装一些东西WITH RECURSIVE才能在SQLAlchemy中工作吗？我的语法实际上是错误的吗？在这里几乎迷失了，任何帮助将不胜感激。

（编辑以使其回到首页。我希望我能说我取得了一些进展，但是我现在不知道该怎么办。这是PostgreSQL vs
SQLite问题吗？有人有可行的示例吗？我可以尝试做的事情？）

Answer 1

问题是您正在运行旧版本的sqlite3（如#sqlalchemy所述）；您拥有3.8.2，并且在3.8.3中添加了CTE支持。