LIMIT

概述

LIMIT子句将别名代表的数据行的前N行数据保留，将其余行舍弃。

语法

limit <N>

• <N>为保留的行数，应为-1或正整数，-1时保留所有数据行

例如，将以下路径查询产生的数据流path的前2行保留：

find().nodes([1, 5]) as nodes
n(nodes).e()[:2].n() as path
limit 2
return path

要留意子句LIMIT和链式命令.limit()参数的区别。下例中，路径查询命令的.limit()参数限制该命令每次执行时仅保留2行结果，该命令一共会执行2次，因此最终结果path包括4行数据：

find().nodes([1, 5]) as nodes
n(nodes).e()[:2].n().limit(2) as path
return path

示例

示例图集

在一个空图集中，依次运行以下各行语句创建示例图集：

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}])

一般用法

本例查找3个age属性值最大@student点，返回他们的name属性：

find().nodes({@student}) as n
order by n.age desc
limit 3
return n.name

Emma
Jason
Pepe