概述

使用语句ORDER BY可根据排序键对数据排序。若有多个排序键出现，则排序操作从左到右依次执行：首先根据第一个键排序；对于第一个键值相同的记录，再按第二个键排序，以此类推。

语法

ORDER BY <key1> <desc_asc?>, <key2?> <desc_asc?>, ...

详情

• <key>：排序键，引用了之前语句中声明的别名。
• <desc_asc?>：排序规范，支持ASC（升序）或DESC（降序）。忽略时默认使用ASC。
• 排序过程自动剔除null值，其对应记录会列在排序结果的末尾。

示例图集

在一个空图集中，逐行运行以下语句，创建示例图集：

create().node_schema("student").node_schema("course").edge_schema("takes")
create().node_property(@*, "name").node_property(@student, "age", int32).node_property(@course, "credits", int32)
insert().into(@student).nodes([{_id:"S1", name:"Jason", age:25}, {_id:"S2", name:"Lina", age:23}, {_id:"S3", name:"Eric", age:24}, {_id:"S4", name:"Emma", age:26}, {_id:"S5", name:"Pepe", age:24}])
insert().into(@course).nodes([{_id:"C1", name:"French", credits:4}, {_id:"C2", name:"Math", credits:5}])
insert().into(@takes).edges([{_from:"S1", _to:"C1"}, {_from:"S2", _to:"C1"}, {_from:"S3", _to:"C1"}, {_from:"S2", _to:"C2"}, {_from:"S3", _to:"C2"}, {_from:"S4", _to:"C2"}, {_from:"S5", _to:"C2"}])

根据属性排序

find().nodes({@student}) as stu
order by stu.age desc
return table(stu.name, stu.age)

结果：

根据点/边别名排序

指定点别名或边别名为分组键时，查询结果将根据点或边的_uuid排序。

find().nodes({@student}) as stu
order by stu
return table(stu.name, stu._uuid)

结果：

根据表达式排序

n({name == "Jason"}).e()[:3].n() as p
order by length(p)
return p{*}

Jason -> French
Jason -> French <- Lina
Jason -> French <- Eric
Jason -> French <- Lina -> Math
Jason -> French <- Eric -> Math

多级排序

n({@course} as crs).e().n({@student} as stu) as p
order by crs.credits, stu.age desc 
return table(crs.name, crs.credits, stu.name, stu.age)

结果：

分组和排序

统计每门课程的注册学生数，并根据统计结果排序：

n({@course} as crs).e().n({@student})
group by crs
with crs, count(crs) as stuCnt
order by stuCnt desc 
return table(crs.name, stuCnt)

结果：