SQL 和 nGQLGraph

基本概念对比Graph

概念名称	SQL	nGQL
vertex	\	vertex
edge	\	edge
vertex type	\	tag
edge type	\	edge type
vertex identifier	\	vid
edge identifier	edge id generated by default	src, dst, rank
column	column	\
row	row	\

语法对比Graph

数据定义语言（DDL）Graph

数据定义语言（DDL）用于定义数据库 schema。 DDL 语句可以创建或修改数据库的结构。

对比项	SQL	nGQL
创建图空间（数据库）	CREATE DATABASE <database_name>	CREATE SPACE <space_name>
列出图空间（数据库）	SHOW DATABASES	SHOW SPACES
使用图空间（数据库）	USE <database_name>	USE <space_name>
删除图空间（数据库）	DROP DATABASE <database_name>	DROP SPACE <space_name>
修改图空间（数据库）	ALTER DATABASE <database_name> alter_option	\
创建 tags/edges	\	CREATE TAG | EDGE <tag_name>
创建表	CREATE TABLE <tbl_name> (create_definition,...)	\
列出表列名	SHOW COLUMNS FROM <tbl_name>	\
列出 tags/edges	\	SHOW TAGS | EDGES
Describe tags/edge	\	DESCRIBE TAG | EDGE <tag_name | edge_name>
修改 tags/edge	\	ALTER TAG | EDGE <tag_name | edge_name>
修改表	ALTER TABLE <tbl_name>	\

索引Graph

对比项	SQL	nGQL
创建索引	CREATE INDEX	CREATE {TAG | EDGE} INDEX
删除索引	DROP INDEX	DROP {TAG | EDGE} INDEX
列出索引	SHOW INDEX FROM	SHOW {TAG | EDGE} INDEXES
重构索引	ANALYZE TABLE	REBUILD {TAG | EDGE} INDEX <index_name> [OFFLINE]

数据操作语言（DML）Graph

数据操作语言（DML）用于操作数据库中的数据。

对比项	SQL	nGQL
插入数据	INSERT IGNORE INTO <tbl_name> [(col_name [, col_name] ...)] {VALUES | VALUE} [(value_list) [, (value_list)]	INSERT VERTEX <tag_name> (prop_name_list[, prop_name_list]) {VALUES | VALUE} vid: (prop_value_list[, prop_value_list]) INSERT EDGE <edge_name> ( <prop_name_list> ) VALUES | VALUE <src_vid> -> <dst_vid>[@<rank>] : ( <prop_value_list> )
查询数据	SELECT	GO, FETCH
更新数据	UPDATE <tbl_name> SET field1=new-value1, field2=new-value2 [WHERE Clause]	UPDATE VERTEX <vid> SET <update_columns> [WHEN <condition>] UPDATE EDGE <edge> SET <update_columns> [WHEN <condition>]
删除数据	DELETE FROM <tbl_name> [WHERE Clause]	DELETE EDGE <edge_type> <vid> -> <vid>[@<rank>] [, <vid> -> <vid> ...] DELETE VERTEX <vid_list>
拼接数据	JOIN	|

数据查询语言（DQL）Graph

数据查询语言（DQL）语句用于执行数据查询。本节说明如何使用 SQL 语句和 nGQL 语句查询数据。

SELECT
 [DISTINCT]
 select_expr [, select_expr] ...
 [FROM table_references]
 [WHERE where_condition]
 [GROUP BY {col_name | expr | position}]
 [HAVING  where_condition]
 [ORDER BY {col_name | expr | position} [ASC | DESC]]

GO [[<M> TO] <N> STEPS ] FROM <node_list>
 OVER <edge_type_list> [REVERSELY] [BIDIRECT]
 [WHERE where_condition]
 [YIELD [DISTINCT] <return_list>]
 [| ORDER BY <expression> [ASC | DESC]]
 [| LIMIT [<offset_value>,] <number_rows>]
 [| GROUP BY {col_name | expr | position} YIELD <col_name>]

<node_list>
   | <vid> [, <vid> ...]
   | $-.id

<edge_type_list>
   edge_type [, edge_type ...]

<return_list>
    <col_name> [AS <col_alias>] [, <col_name> [AS <col_alias>] ...]

数据控制语言（DCL）Graph

数据控制语言（DCL）包含诸如 GRANT 和 REVOKE 之类的命令，这些命令主要用来处理数据库系统的权限，其他控件。

对比项	SQL	nGQL
创建用户	CREATE USER	CREATE USER
删除用户	DROP USER	DROP USER
更改密码	SET PASSWORD	CHANGE PASSWORD
授予权限	GRANT <priv_type> ON [object_type] TO <user>	GRANT ROLE <role_type> ON <space> TO <user>
删除权限	REVOKE <priv_type> ON [object_type] TO <user>	REVOKE ROLE <role_type> ON <space> FROM <user>

数据模型Graph

查询语句基于以下数据模型：

MySQLGraph

NebulaGraphGraph

增删改查（CRUD）Graph

本节介绍如何使用 SQL 和 nGQL 语句创建（C）、读取（R）、更新（U）和删除（D）数据。

插入数据Graph

mysql> INSERT INTO player VALUES (100, 'Tim Duncan', 42);

nebula> INSERT VERTEX player(name, age) VALUES 100: ('Tim Duncan', 42);

查询数据Graph

Find the player whose id is 100 and output the name property:

mysql> SELECT player.name FROM player WHERE player.id = 100;

nebula> FETCH PROP ON player 100 YIELD player.name;

更新数据Graph

mysql> UPDATE player SET name = 'Tim';

nebula> UPDATE VERTEX 100 SET player.name = "Tim";

删除数据Graph

mysql> DELETE FROM player WHERE name = 'Tim';

nebula> DELETE VERTEX 121;
nebula> DELETE EDGE follow 100 -> 200;

示例查询Graph

示例 1Graph

返回年龄超过 36 岁的球员。

mysql> SELECT player.name
FROM player
WHERE player.age < 36;

使用 nGQL 查询有些不同，因为您必须在过滤属性之前创建索引。更多信息请参见 Graph。

nebula> CREATE TAG INDEX player_age ON player(age);
nebula> REBUILD TAG INDEX player_age OFFLINE;
nebula> LOOKUP ON player WHERE player.age < 36;

示例 2Graph

查找球员 Tim Duncan 并返回他效力的所有球队。

mysql> SELECT a.id, a.name, c.name
FROM player a
JOIN serve b ON a.id=b.player_id
JOIN team c ON c.id=b.team_id
WHERE a.name = 'Tim Duncan';

nebula> CREATE TAG INDEX player_name ON player(name);
nebula> REBUILD TAG INDEX player_name OFFLINE;
nebula> LOOKUP ON player WHERE player.name == 'Tim Duncan' YIELD player.name AS name | GO FROM $-.VertexID OVER serve YIELD $-.name, $$.team.name;

示例 3Graph

查找球员 Tim Duncan 的队友。

mysql> SELECT a.id, a.name, c.name
FROM player a
JOIN serve b ON a.id=b.player_id
JOIN team c ON c.id=b.team_id
WHERE c.name IN (SELECT c.name
FROM player a
JOIN serve b ON a.id=b.player_id
JOIN team c ON c.id=b.team_id
WHERE a.name = 'Tim Duncan');

在 nGQL 中，我们使用管道将上一条语句的输出作为下一条语句的输入。

nebula> GO FROM 100 OVER serve YIELD serve._dst AS Team | GO FROM $-.Team OVER serve REVERSELY YIELD $$.player.name;

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最后更新: July 21, 2020