LOOKUP 语法

LOOKUP 语句指定过滤条件对数据进行查询。LOOKUP 语句之后通常跟着 WHERE 子句。WHERE 子句用于向条件中添加过滤性的谓词,从而对数据进行过滤。

注意: 在使用 LOOKUP 语句之前,请确保已创建索引。查看索引文档了解有关索引的更多信息。

LOOKUP ON {<vertex_tag> | <edge_type>} WHERE <expression> [ AND | OR expression ...]) ] [YIELD <return_list>]

<return_list>
    <col_name> [AS <col_alias>] [, <col_name> [AS <col_alias>] ...]
  • LOOKUP 语句用于寻找点或边的集合。
  • WHERE 指定被筛选的逻辑条件。同样支持逻辑关键词 AND、OR、NOT,详情参见 WHERE 的用法。 注意: WHERE 子句在 LOOKUP 中暂不支持如下操作:
    • $-$^
    • 在关系表达式中,暂不支持操作符两边都是field-name 的表达式,如 (tagName.column1 > tagName.column2)
    • 暂不支持运算表达式和 function 表达式中嵌套 AliasProp 表达式。
  • YIELD 指定返回结果。如未指定,则在 LOOKUP 标签时返回点 ID,在 LOOKUP 边类型时返回边的起点 ID、终点 ID 和 ranking 值。

点查询

如下示例返回名称为 Tony Parker,标签为 player 的顶点。

nebula> CREATE TAG INDEX index_player ON player(name, age);

nebula> LOOKUP ON player WHERE player.name == "Tony Parker";
============
| VertexID |
============
| 101      |
------------

nebula> LOOKUP ON player WHERE player.name == "Tony Parker" \
YIELD player.name, player.age;
=======================================
| VertexID | player.name | player.age |
=======================================
| 101      | Tony Parker | 36         |
---------------------------------------

nebula> LOOKUP ON player WHERE player.name== "Kobe Bryant" YIELD player.name AS name | \
GO FROM $-.VertexID OVER serve YIELD $-.name, serve.start_year, serve.end_year, $$.team.name;
==================================================================
| $-.name     | serve.start_year | serve.end_year | $$.team.name |
==================================================================
| Kobe Bryant | 1996             | 2016           | Lakers       |
------------------------------------------------------------------

边查询

如下示例返回 degree 为 90,边类型为 follow 的边。

nebula> CREATE EDGE INDEX index_follow ON follow(degree);

nebula> LOOKUP ON follow WHERE follow.degree == 90;
=============================
| SrcVID | DstVID | Ranking |
=============================
| 100    | 106    | 0       |
-----------------------------

nebula> LOOKUP ON follow WHERE follow.degree == 90 YIELD follow.degree;
=============================================
| SrcVID | DstVID | Ranking | follow.degree |
=============================================
| 100    | 106    | 0       | 90            |
---------------------------------------------

nebula> LOOKUP ON follow WHERE follow.degree == 60 YIELD follow.degree AS Degree | \
GO FROM $-.DstVID OVER serve YIELD $-.DstVID, serve.start_year, serve.end_year, $$.team.name;
================================================================
| $-.DstVID | serve.start_year | serve.end_year | $$.team.name |
================================================================
| 105       | 2010             | 2018           | Spurs        |
----------------------------------------------------------------
| 105       | 2009             | 2010           | Cavaliers    |
----------------------------------------------------------------
| 105       | 2018             | 2019           | Raptors      |
----------------------------------------------------------------