WHERE 可以将别名中满足条件的数据行保留,不满足条件的数据行舍弃。
语法 1:WHERE <condition>
语法 2:WHERE <query>
(开发中)
参数:
- <condition>:判断条件表达式,为真的行被保留
- <query>:查询语句,有查询结果的行被保留
WHERE 子句后所接的语句须对流入 WHERE 语句的别名、或该别名的同源别名进行操作,否则该语句无效。
例如,将两个不同源的点 n1、n2 进行比较,如果颜色相同则返回:
find().nodes({shape == "square"}) as n1
find().nodes({shape == "round"}) as n2
where n1.color == n2.color
return n1, n2
用条件表达式进行判断
示例图集:(以下示例将在本图基础上运行)
在空图集中依次运行以下各行代码以创建该图数据:create().node_schema("student").node_schema("course")
create().node_property(@*, "name").node_property(@student, "age", int32).node_property(@course, "credit", int32)
insert().into(@student).nodes([{_id:"S001", _uuid:1, name:"Jason", age:25}, {_id:"S002", _uuid:2, name:"Lina", age:23}, {_id:"S003", _uuid:3, name:"Eric", age:24}, {_id:"S004", _uuid:4, name:"Emma", age:26}, {_id:"S005", _uuid:5, name:"Pepe", age:24}])
insert().into(@course).nodes([{_id:"C001", _uuid:6, name:"French", credit:4}, {_id:"C002", _uuid:7, name:"Math", credit:5}])
insert().into(@default).edges([{_uuid:1, _from_uuid:1, _to_uuid:6}, {_uuid:2, _from_uuid:2, _to_uuid:6}, {_uuid:3, _from_uuid:3, _to_uuid:6}, {_uuid:4, _from_uuid:2, _to_uuid:7}, {_uuid:5, _from_uuid:3, _to_uuid:7}, {_uuid:6, _from_uuid:4, _to_uuid:7}, {_uuid:7, _from_uuid:5, _to_uuid:7}])
示例:查询 1 步路径 课程-学生,如果课程的 credit 为 4,或者学生的 age 为 24时,则返回该路径,携带全部属性
n({@course} as a).e().n({@student} as b) as p
where a.credit == 4 || b.age == 24
return p{*}
French <---- Jason
French <---- Lina
French <---- Eric
Math <---- Pepe
Math <---- Eric
用查询语句进行判断 (开发中)
示例:查找满足下图所示条件的中介银行卡 agent,即 CA002 经由 agent 向 CA001 转账,并且 agent 是 CA003 的 2Hop 以内的邻居:
n({_id == "CA002"}).re().n({@card} as agent).re().n({_id == "CA001"})
where n(agent).e()[*:2].n({_id == "CA003"})
return agent{*}
分析:WHERE 子句对模板查询语句输出的别名 agent 做进一步过滤,对每一个 agent 查找其到 CA003 的 2 步以内的最短路径是否存在,如果存在,则将该 agent 传给后面的 RETURN。
上面的例子可以用子图模板改写为:
graph([
n({_id == "CA002"}).re().n({@card} as agent).re().n({_id == "CA001"}),
n(agent).e()[*:2].n({_id == "CA003"})
])
return agent{*}