Question

我正在尝试使用SQLAlchemy进行Pylons，我喜欢它，只有一件事，是否可以在执行之前打印出从Table（）。create（）生成的原始SQL CREATE TABLE数据？

Answer 1

from sqlalchemy.schema import CreateTable

print(CreateTable(table))

如果您使用声明性语法：

print(CreateTable(Model.__table__))

<强>更新

由于我已接受答案并且klenwell answer中有重要信息，我也会在此处添加。

您可以通过编译引擎来获取特定数据库（MySQL，Postgresql等）的SQL。

print(CreateTable(Model.__table__).compile(engine))

更新2：

@jackotonye在评论中添加了一种没有引擎的方法。

print(CreateTable(Model.__table__).compile(dialect=postgresq‌l.dialect()))

Answer 2

我需要获取原始表sql以便为某些现有模型设置测试。这是我基于Antoine's answer为SQLAlchemy 0.7.4创建的成功单元测试作为概念证明：

from sqlalchemy import create_engine
from sqlalchemy.schema import CreateTable
from model import Foo

sql_url = "sqlite:///:memory:"    
db_engine = create_engine(sql_url)

table_sql = CreateTable(Foo.table).compile(db_engine)
self.assertTrue("CREATE TABLE foos" in str(table_sql))

Answer 3

您可以使用以下命令设置引擎以转储元数据创建序列：

X_train: (90, 20) y_train: (90,)
X_test: (10, 20) y_test: (10,)

此方法的一个优点是枚举和索引包含在打印输出中。使用def metadata_dump(sql, *multiparams, **params): # print or write to log or file etc print(sql.compile(dialect=engine.dialect)) engine = create_engine(myDatabaseURL, strategy='mock', executor=metadata_dump) metadata.create_all(engine)就可以了。

另一个优点是模式定义的顺序是正确的，并且（几乎）可用作脚本。

Answer 4

这样的东西？（来自SQLA FAQ）

http://docs.sqlalchemy.org/en/latest/faq/sqlexpressions.html

Answer 5

事实证明这是直截了当的：

from sqlalchemy.dialects import postgresql
from sqlalchemy.schema import CreateTable
from sqlalchemy import Table, Column, String, MetaData

metadata = MetaData()

users = Table('users', metadata,
              Column('username', String)
)

statement = CreateTable(users)

print(statement.compile(dialect=postgresql.dialect()))

输出：

CREATE TABLE users (
    username VARCHAR
)

更进一步，它甚至可以在预准备语句中支持绑定参数。

参考

如何将SQL表达式呈现为字符串，可能使用内联绑定参数？

...

或没有引擎：
from sqlalchemy.dialects import postgresql
print(statement.compile(dialect=postgresql.dialect()))

消息来源：http://docs.sqlalchemy.org/en/latest/faq/sqlexpressions.html#faq-sql-expression-string

示例：使用SQL Alchemy生成用户重命名脚本

#!/usr/bin/env python
import csv
from sqlalchemy.dialects import postgresql
from sqlalchemy import bindparam, Table, Column, String, MetaData

metadata = MetaData()

users = Table('users', metadata,
              Column('username', String)
)

renames = []

with open('users.csv') as csvfile:
    for row in csv.DictReader(csvfile):
        renames.append({
            'from': row['sAMAccountName'],
            'to': row['mail']
        })

for rename in renames:
    stmt = (users.update()
            .where(users.c.username == rename['from'])
            .values(username=rename['to']))
    print(str(stmt.compile(dialect=postgresql.dialect(),
                           compile_kwargs={"literal_binds": True})) + ';')

处理此users.csv时：

sAMAccountName,mail
bmcboatface,boaty.mcboatface@example.com
ndhyani,naina.dhyani@contoso.com

给出如下输出：

UPDATE users SET username='boaty.mcboatface@example.com' WHERE users.username = 'bmcboatface';
UPDATE users SET username='naina.dhyani@contoso.com' WHERE users.username = 'ndhyani';users.username = 'ndhyani';

为什么研究船只有电子邮件地址尚未确定。我与Example Inc的IT团队保持联系并且没有回复。

Answer 6

您可能是sqlalchemy.create_engine的echo参数吗？

/ tmp $ cat test_s.py

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class Department(Base):
    __tablename__ = "departments"

    department_id = sa.Column(sa.types.Integer, primary_key=True)
    name = sa.Column(sa.types.Unicode(100), unique=True)
    chief_id = sa.Column(sa.types.Integer)
    parent_department_id = sa.Column(sa.types.Integer,
                                     sa.ForeignKey("departments.department_id"))

    parent_department = sa.orm.relation("Department")


engine = sa.create_engine("sqlite:///:memory:", echo=True)
Base.metadata.create_all(bind=engine)

/ tmp $ python test_s.py

2011-03-24 15:09:58,311 INFO sqlalchemy.engine.base.Engine.0x...42cc PRAGMA table_info("departments")
2011-03-24 15:09:58,312 INFO sqlalchemy.engine.base.Engine.0x...42cc ()
2011-03-24 15:09:58,312 INFO sqlalchemy.engine.base.Engine.0x...42cc 
CREATE TABLE departments (
    department_id INTEGER NOT NULL, 
    name VARCHAR(100), 
    chief_id INTEGER, 
    parent_department_id INTEGER, 
    PRIMARY KEY (department_id), 
    UNIQUE (name), 
    FOREIGN KEY(parent_department_id) REFERENCES departments (department_id)
)

2011-03-24 15:09:58,312 INFO sqlalchemy.engine.base.Engine.0x...42cc ()
2011-03-24 15:09:58,312 INFO sqlalchemy.engine.base.Engine.0x...42cc COMMIT

SQLAlchemy从create（）打印原始SQL

6 个答案:

参考

示例：使用SQL Alchemy生成用户重命名脚本