SQLAlchemy 几种查询方式总结

原文链接：https://my.oschina.net/freegeek/blog/222725

几种常见sqlalchemy查询：

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<code class="hljs python">    <span class="hljs-comment">#简单查询     print(session.query(User).all())     print(session.query(User.name, User.fullname).all())     print(session.query(User, User.name).all())           <span class="hljs-comment">#带条件查询     print(session.query(User).filter_by(name=<span class="hljs-string">'user1').all())     print(session.query(User).filter(User.name == <span class="hljs-string">"user").all())     print(session.query(User).filter(User.name.like(<span class="hljs-string">"user%")).all())           <span class="hljs-comment">#多条件查询     print(session.query(User).filter(and_(User.name.like(<span class="hljs-string">"user%"), User.fullname.like(<span class="hljs-string">"first%"))).all())     print(session.query(User).filter(or_(User.name.like(<span class="hljs-string">"user%"), User.password != <span class="hljs-keyword">None)).all())           <span class="hljs-comment">#sql过滤     print(session.query(User).filter(<span class="hljs-string">"id>:id").params(id=<span class="hljs-number">1).all())           <span class="hljs-comment">#关联查询      print(session.query(User, Address).filter(User.id == Address.user_id).all())     print(session.query(User).join(User.addresses).all())     print(session.query(User).outerjoin(User.addresses).all())           <span class="hljs-comment">#聚合查询     print(session.query(User.name, func.count(<span class="hljs-string">'*').label(<span class="hljs-string">"user_count")).group_by(User.name).all())     print(session.query(User.name, func.sum(User.id).label(<span class="hljs-string">"user_id_sum")).group_by(User.name).all())           <span class="hljs-comment">#子查询     stmt = session.query(Address.user_id, func.count(<span class="hljs-string">'*').label(<span class="hljs-string">"address_count")).group_by(Address.user_id).subquery()     print(session.query(User, stmt.c.address_count).outerjoin((stmt, User.id == stmt.c.user_id)).order_by(User.id).all())           <span class="hljs-comment">#exists     print(session.query(User).filter(exists().where(Address.user_id == User.id)))     print(session.query(User).filter(User.addresses.any()))</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></code>

限制返回字段查询

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<code class="hljs nginx"><span class="hljs-attribute">person = session.query(Person.name, Person.created_at,                                   Person.updated_at).filter_by(name=<span class="hljs-string">"zhongwei").order_by(                          Person.created_at).first()</span></span></code>

记录总数查询：

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<code class="hljs swift">from sqlalchemy <span class="hljs-keyword">import func   # <span class="hljs-built_in">count <span class="hljs-type">User records, without # using a subquery. session.query(<span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">func<span class="hljs-function">.<span class="hljs-title"><span class="hljs-function"><span class="hljs-title">count<span class="hljs-params"><span class="hljs-function"><span class="hljs-params">(User.id))   # <span class="hljs-keyword">return <span class="hljs-built_in">count of user <span class="hljs-string">"id" grouped # by <span class="hljs-string">"name" session.query(<span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">func<span class="hljs-function">.<span class="hljs-title"><span class="hljs-function"><span class="hljs-title">count<span class="hljs-params"><span class="hljs-function"><span class="hljs-params">(User.id)).         group_by(<span class="hljs-type">User.name)   from sqlalchemy <span class="hljs-keyword">import distinct   # <span class="hljs-built_in">count distinct <span class="hljs-string">"name" values session.query(<span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">func<span class="hljs-function">.<span class="hljs-title"><span class="hljs-function"><span class="hljs-title">count<span class="hljs-params"><span class="hljs-function"><span class="hljs-params">(distinct<span class="hljs-params"><span class="hljs-function"><span class="hljs-params"><span class="hljs-params">(User.name)))</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></code>