Implement the multi query parts of openCypher

docs-2.0/2.quick-start/6.cheatsheet-for-ngql-command.md

@@ -296,7 +296,7 @@
 
 
 
-* [UNWIND](../3.ngql-guide/7.general-query-statements/7.unwind.md)
+* [UNWIND](../3.ngql-guide/8.clauses-and-options/unwind.md)
 
   ```
   UNWIND <list> AS <alias> <RETURN clause>

docs-2.0/3.ngql-guide/1.nGQL-overview/3.graph-patterns.md

@@ -54,10 +54,6 @@
 (a:User:Admin)-[]->(b)
 ```
 
-!!! compatibility "openCypher 兼容性"
-
-    nGQL 中的`MATCH`语句不支持用`(a:User:Admin)`匹配多个标签。如需匹配多标签可使用过滤条件，如`WHERE "User" IN tags(n) AND "Admin" IN tags(n)`。
-
 ## 属性模式
 
 点和边是图的基本结构。nGQL 在这两种结构上都可以增加属性，方便实现更丰富的模型。

docs-2.0/3.ngql-guide/7.general-query-statements/2.match.md

@@ -2,7 +2,7 @@
 
 `MATCH`语句提供基于模式（pattern）匹配的搜索功能。
 
-一个`MATCH`语句定义了一个[搜索模式](../1.nGQL-overview/3.graph-patterns.md)，用该模式匹配存储在 Nebula Graph 中的数据，然后用`RETURN`子句检索数据。
+一个`MATCH`语句定义了一个搜索模式，用该模式匹配存储在 Nebula Graph 中的数据，然后用`RETURN`子句检索数据。
 
 本文示例使用测试数据集 [basketballplayer](../1.nGQL-overview/1.overview.md#basketballplayer) 进行演示。
 
@@ -11,9 +11,21 @@
 与`GO`或`LOOKUP`等其他查询语句相比，`MATCH`的语法更灵活。`MATCH`语法可以概括如下：
 
 ```ngql
-MATCH <pattern> [<WHERE clause>] RETURN <output>;
+MATCH <pattern> [<clause_1>]  RETURN <output>  [<clause_2>];
 ```
 
+- `pattern`：pattern 的详细说明请参见[模式](../1.nGQL-overview/3.graph-patterns.md)。`MATCH`语句支持匹配一个或多个模式，多个模式之间用英文逗号（,）分隔。例如`(a)-[]->(b),(c)-[]->(d)`。
+
+- `clause_1`：支持`WHERE`、`WITH`、`UNWIND`、`OPTIONAL MATCH`子句，也可以使用`MATCH`作为子句。
+
+- `output`：定义需要返回的输出。可以使用`AS`设置输出的别名。
+
+  !!! compatibility "历史版本兼容性"
+
+        从3.0版本开始，`pattern`支持同时匹配多个 Tag、Edge Type，所以返回属性时，需要额外指定 Tag/Edge type 名称。即从`RETURN 变量名.属性名`改为`RETURN 变量名.Tag.属性名`或`RETURN 变量名.Edge_type.属性名`。
+
+- `clause_2`：支持`ORDER BY`、`LIMIT`子句。
+
 ## MATCH 工作流程
 
 1. `MATCH`语句使用原生索引查找起始点或边，起始点或边可以在模式的任何位置。即一个有效的`MATCH`语句，**必须有一个属性、Tag 或 Edge type 已经创建索引，或者在`WHERE`子句中用 id() 函数指定了特定点的 VID**。如何创建索引，请参见[创建原生索引](../14.native-index-statements/1.create-native-index.md)。
@@ -108,6 +120,21 @@ nebula> MATCH (v:player) \
 ...
 ```
 
+需要匹配拥有多个 Tag 的点，可以用英文冒号（:）。
+
+```ngql
+nebula> CREATE TAG actor (name string, age int);
+nebula> INSERT VERTEX actor(name, age) VALUES "player100":("Tim Duncan", 42);
+nebula> MATCH (v:player:actor) \
+        RETURN v \
+        LIMIT 10;
++----------------------------------------------------------------------------------------+
+| v                                                                                      |
++----------------------------------------------------------------------------------------+
+| ("player100" :actor{age: 42, name: "Tim Duncan"} :player{age: 42, name: "Tim Duncan"}) |
++----------------------------------------------------------------------------------------+
+```
+
 ### 匹配点的属性
 
 !!! Note
@@ -131,7 +158,7 @@ nebula> MATCH (v:player{name:"Tim Duncan"}) \
 
 ```ngql
 nebula> MATCH (v:player) \
-        WHERE v.name == "Tim Duncan" \
+        WHERE v.player.name == "Tim Duncan" \
         RETURN v;
 +----------------------------------------------------+
 | v                                                  |
@@ -169,6 +196,7 @@ nebula> MATCH (v:player { name: 'Tim Duncan' })--(v2) \
 | v2                                                        |
 +-----------------------------------------------------------+
 | ("player101" :player{age: 36, name: "Tony Parker"})       |
+| ("player101" :player{age: 36, name: "Tony Parker"})       |
 | ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
 +-----------------------------------------------------------+
 ```
@@ -182,38 +210,56 @@ nebula> MATCH (v:player { name: 'Tim Duncan' })--(v2) \
     在 nGQL 1.x 中，`--`符号用于行内注释，在 nGQL 2.x 中，`--`符号表示出边或入边，不再用于注释。
 
 ```ngql
-nebula> MATCH (v:player{name:"Tim Duncan"})--(v2) \
-        RETURN v2.name AS Name;
+nebula> MATCH (v:player{name:"Tim Duncan"})--(v2:player) \
+        RETURN v2.player.name AS Name;
 +---------------------+
 | Name                |
 +---------------------+
-| "Spurs"             |
-| "Tony Parker"       |
-| "LaMarcus Aldridge" |
-| "Marco Belinelli"   |
+| "Manu Ginobili"     |
+| "Manu Ginobili"     |
+| "Dejounte Murray"   |
 ...
 ```
 
 用户可以在`--`符号上增加`<`或`>`符号指定边的方向。
 
 ```ngql
 # -->表示边从 v 开始，指向 v2。对于点 v 来说是出边，对于点 v2 来说是入边。
-nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2) \
-        RETURN v2.name AS Name;
+nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2:player) \
+        RETURN v2.player.name AS Name;
 +-----------------+
 | Name            |
 +-----------------+
-| "Spurs"         |
 | "Tony Parker"   |
 | "Manu Ginobili" |
 +-----------------+
 ```
 
+如果需要判断目标点，可以使用`CASE`表达式。
+
+```ngql
+nebula> MATCH (v:player{name:"Tim Duncan"})--(v2) \
+        RETURN \
+        CASE WHEN v2.team.name IS NOT NULL \
+        THEN v2.team.name  \
+        WHEN v2.player.name IS NOT NULL \
+        THEN v2.player.name END AS Name;
+
++---------------------+
+| Name                |
++---------------------+
+| "Manu Ginobili"     |
+| "Manu Ginobili"     |
+| "Spurs"             |
+| "Dejounte Murray"   |
+...
+```
+
 如果需要扩展模式，可以增加更多点和边。
 
 ```ngql
 nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2)<--(v3) \
-        RETURN v3.name AS Name;
+        RETURN v3.player.name AS Name;
 +---------------------+
 | Name                |
 +---------------------+
@@ -227,7 +273,7 @@ nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2)<--(v3) \
 
 ```ngql
 nebula> MATCH (v:player{name:"Tim Duncan"})-->()<--(v3) \
-        RETURN v3.name AS Name;
+        RETURN v3.player.name AS Name;
 +---------------------+
 | Name                |
 +---------------------+
@@ -441,6 +487,20 @@ nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow|serve*2]->(v2) \
 +-----------------------------------------------------------+
 ```
 
+### 匹配多个模式
+
+用户可以用英文逗号（,）分隔多个模式。
+
+```
+nebula> MATCH (v1:player{name:"Tim Duncan"}), (v2:team{name:"Spurs"}) \
+        RETURN v1,v2;
++----------------------------------------------------+----------------------------------+
+| v1                                                 | v2                               |
++----------------------------------------------------+----------------------------------+
+| ("player100" :player{age: 42, name: "Tim Duncan"}) | ("team204" :team{name: "Spurs"}) |
++----------------------------------------------------+----------------------------------+
+```
+
 ## 常用检索操作
 
 ### 检索点或边的信息
@@ -513,19 +573,19 @@ nebula> MATCH (v:player{name:"Tim Duncan"}) \
 
 ```ngql
 nebula> MATCH (v:player{name:"Tim Duncan"}) \
-        RETURN v.age;
-+-------+
-| v.age |
-+-------+
-| 42    |
-+-------+
+        RETURN v.player.age;
++--------------+
+| v.player.age |
++--------------+
+| 42           |
++--------------+
 ```
 
 使用`AS`设置属性的别名。
 
 ```ngql
 nebula> MATCH (v:player{name:"Tim Duncan"}) \
-        RETURN v.age AS Age;
+        RETURN v.player.age AS Age;
 +-----+
 | Age |
 +-----+
@@ -636,6 +696,26 @@ nebula> MATCH p=(v:player{name:"Tim Duncan"})-[*..2]->(v2) \
 +------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------+
 ```
 
+### 多MATCH检索
+
+不同的模式有不同的筛选条件时，可以使用多`MATCH`，会返回模式完全匹配的行。
+
+```ngql
+nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
+        MATCH (n)-[]->(l) WHERE id(n)=="player125" \
+        RETURN id(m),id(n),id(l);
++-------------+-------------+-------------+
+| id(m)       | id(n)       | id(l)       |
++-------------+-------------+-------------+
+| "player100" | "player125" | "team204"   |
+| "player100" | "player125" | "player100" |
++-------------+-------------+-------------+
+```
+
+### OPTIONAL MATCH检索
+
+参见[OPTIONAL MATCH](../8.clauses-and-options/optional-match.md)。
+
 !!! Performance
 
     Nebula Graph 中`MATCH`语句的性能和资源占用得到了优化，但对性能要求较高时，仍建议使用 `GO`, `LOOKUP`, `|` 和 `FETCH` 等来替代`MATCH`。

docs-2.0/3.ngql-guide/8.clauses-and-options/optional-match.md

@@ -0,0 +1,39 @@
+# OPTIONAL MATCH
+
+`OPTIONAL MATCH`通常用于`MATCH`语句中，作为`MATCH`语句的可选项去匹配图数据库中的模式，如果图数据库中没有对应的模式，对应的列返回`NULL`。
+
+## openCypher 兼容性
+
+本文操作仅适用于 nGQL 中的 openCypher 方式。
+
+## 示例
+
+`MATCH`语句中使用`OPTIONAL MATCH`的示例如下：
+
+```ngql
+nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
+        OPTIONAL MATCH (n)-[]->(l) WHERE id(n)=="player125" \
+        RETURN id(m),id(n),id(l);
++-------------+-------------+-------------+
+| id(m)       | id(n)       | id(l)       |
++-------------+-------------+-------------+
+| "player100" | "team204"   | __NULL__    |
+| "player100" | "player101" | __NULL__    |
+| "player100" | "player125" | "team204"   |
+| "player100" | "player125" | "player100" |
++-------------+-------------+-------------+
+```
+
+而使用多`MATCH`，不使用`OPTIONAL MATCH`时，会返回模式完全匹配的行。示例如下：
+
+```ngql
+nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
+        MATCH (n)-[]->(l) WHERE id(n)=="player125" \
+        RETURN id(m),id(n),id(l);
++-------------+-------------+-------------+
+| id(m)       | id(n)       | id(l)       |
++-------------+-------------+-------------+
+| "player100" | "player125" | "team204"   |
+| "player100" | "player125" | "player100" |
++-------------+-------------+-------------+
+```

docs-2.0/3.ngql-guide/7.general-query-statements/7.unwind.md → docs-2.0/3.ngql-guide/8.clauses-and-options/unwind.md

@@ -63,11 +63,11 @@ nebula> MATCH p=(v:player{name:"Tim Duncan"})--(v2) \
 +----------------------------------------------------------------------------------------------------------------------+
 | collect(r)                                                                                                           |
 +----------------------------------------------------------------------------------------------------------------------+
-| [("player100" :player{age: 42, name: "Tim Duncan"}), ("player101" :player{age: 36, name: "Tony Parker"}),
-("team204" :team{name: "Spurs"}), ("player102" :player{age: 33, name: "LaMarcus Aldridge"}),
-("player125" :player{age: 41, name: "Manu Ginobili"}), ("player104" :player{age: 32, name: "Marco Belinelli"}),
-("player144" :player{age: 47, name: "Shaquile O'Neal"}), ("player105" :player{age: 31, name: "Danny Green"}),
-("player113" :player{age: 29, name: "Dejounte Murray"}), ("player107" :player{age: 32, name: "Aron Baynes"}),
-("player109" :player{age: 34, name: "Tiago Splitter"}), ("player108" :player{age: 36, name: "Boris Diaw"})] |
+| [("player100" :player{age: 42, name: "Tim Duncan"}), ("player101" :player{age: 36, name: "Tony Parker"}),            |
+|("team204" :team{name: "Spurs"}), ("player102" :player{age: 33, name: "LaMarcus Aldridge"}),                          |
+|("player125" :player{age: 41, name: "Manu Ginobili"}), ("player104" :player{age: 32, name: "Marco Belinelli"}),       |
+|("player144" :player{age: 47, name: "Shaquile O'Neal"}), ("player105" :player{age: 31, name: "Danny Green"}),         |
+|("player113" :player{age: 29, name: "Dejounte Murray"}), ("player107" :player{age: 32, name: "Aron Baynes"}),         |
+|("player109" :player{age: 34, name: "Tiago Splitter"}), ("player108" :player{age: 36, name: "Boris Diaw"})]           |  
 +----------------------------------------------------------------------------------------------------------------------+
 ```

mkdocs.yml

@@ -197,7 +197,6 @@ nav:
           - LOOKUP: 3.ngql-guide/7.general-query-statements/5.lookup.md
           - GO: 3.ngql-guide/7.general-query-statements/3.go.md
           - FETCH: 3.ngql-guide/7.general-query-statements/4.fetch.md
-          - UNWIND: 3.ngql-guide/7.general-query-statements/7.unwind.md
           - SHOW:
             - SHOW CHARSET: 3.ngql-guide/7.general-query-statements/6.show/1.show-charset.md
             - SHOW COLLATION: 3.ngql-guide/7.general-query-statements/6.show/2.show-collation.md
@@ -227,6 +226,8 @@ nav:
           - WHERE: 3.ngql-guide/8.clauses-and-options/where.md
           - YIELD: 3.ngql-guide/8.clauses-and-options/yield.md
           - WITH: 3.ngql-guide/8.clauses-and-options/with.md
+          - UNWIND: 3.ngql-guide/8.clauses-and-options/unwind.md
+          - OPTIONAL MATCH: 3.ngql-guide/8.clauses-and-options/optional-match.md
 
       - 图空间语句:
           - CREATE SPACE: 3.ngql-guide/9.space-statements/1.create-space.md