如何使用 SQLAlchemy 进行批量“SELECT”查询？

Question

我有一个简单的查询：

query = """SELECT (A.name, A.food) FROM animals AS A
    WHERE
        A.type = :animal_type AND M.id = :member_id
    INNER JOIN members as M ON M.animal_id = A.animal_id;"""

我有一个输入列表，例如：

animals_memberships = [
    {
        "animal_type": "BEAR",
        "member_id": 100,
    },
    {
        "animal_type": "RAT",
        "member_id": 200,
    },
    ...
]

目前，我正在遍历每个动物成员并查询数据：

queries = []
for item in animals_memberships:
    session.execute(
        query, {
            "member_id": item["member_id"],
            "animal_type": item["animal_type"],
        }
    )

animal_names_foods = [
    result.fetchall()[0] for result in queries
]

是否可以执行“批量”查询，类似于批量插入如何使用 session.bulk_save_objects()？

Answer 1

您可以像这样在一次查询中获取所有数据

SELECT (A.name, A.food) FROM animals AS A
    WHERE
        (A.type, M.id) in (VALUES ('BEAR', 100), ('RAT', 200))
    INNER JOIN members as M ON M.animal_id = A.animal_id;

顺便问一下，如何在 python

中以安全的方式构建此查询

animals_memberships = [
    {
        "member_id": 100,
        "animal_type": "BEAR",
    },
    {
        "member_id": 200,
        "animal_type": "RAT",
    },
]

parts = []
params = {}

for idx, item in enumerate(animals_memberships):
    params[f"member_id_{idx}"] = item["member_id"]
    params[f"animal_type_{idx}"] = item["animal_type"]
    parts.append(f"(:member_id_{idx}, :animal_type_{idx})")

parts_str = ",".join(parts)

query = f"""
    SELECT (A.name, A.food) FROM animals AS A
    WHERE
        (A.type, M.id) IN (VALUES {parts_str})
    INNER JOIN members as M ON M.animal_id = A.animal_id;
"""

session.execute(query, params)

如何使用 SQLAlchemy 进行批量“SELECT”查询？

How to make bulk `SELECT` queries with SQLAlchemy?

sql

postgresql

sqlalchemy