sql - 如何用': syntax error"in recursive CTE query (flask/sqlalchemy)修复 "near '

Question

我正在尝试重现 this在 SqlAlchemy 文档页面上找到的查询。在 models.py 中设置 Part 类后，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(从错误消息中复制粘贴)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，在不同的地方换行):

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，为了比较，这里是 sqlalchemy 文档 link 的纯 PostgreSQL 查询到:

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

我能看到的 Postgre 查询(我假设它应该有效)和我生成的查询之间的唯一区别是:

1. 所有额外的“AS”语句(SELECT parts.sub_part AS sub_part vs SELECT sub_part)
2. 不同的格式(生成的查询在奇怪的地方有换行符 - 例如，UNION ALL 和 SELECT 之间没有换行符)

但是，据我所知，这些都不应该导致语法错误...... 我还尝试将 Postgre 查询作为原始 SQL 执行(尽管 SQLAlchemy 显然使用了 sqlite3，但仍然如此):

    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()

但我仍然遇到语法错误。

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，结果相似。

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...似乎即使是语法正确的 WITH 查询仍会抛出错误。我知道 Sqlalchemy 支持递归 CTE 查询，根据文档和这里 (_http://stackoverflow.com/a/24780445) 的回答。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 代码实际上与文档中的示例相同。

我是否需要为 WITH RECURSIVE 安装一些东西才能在 SQLAlchemy 中工作？我的语法真的错了吗？几乎迷失在这里，任何帮助表示赞赏。

(编辑以将其返回到首页。我希望我可以说我已经取得了一些进展，但我现在真的不知道该做什么。这是 PostgreSQL 与 SQLite 的问题吗？有没有人有我正在尝试做的工作示例，我可以看看吗？)

Answer 1

问题是您运行的是旧版本的 sqlite3(如#sqlalchemy 中所讨论)；你有 3.8.2 并且在 3.8.3 中添加了 CTE 支持。