# GQL兼容性
GQL标准请参考ISO发布的[GQL文档](https://www.iso.org/standard/76120.html)。GES对GQL的最小化支持（GQL minimum conformance）如下所示：
1. 支持特性GG02"Graph with a closed graph type"以及GG20"Explicit element type names"。
2. 支持Unicode 13。
3. 支持基础数据类型，包括：STRING，BOOLEAN，INT，FLOAT。
4. 支持一系列特性，详见[支持的特性清单]。
 #### 支持的特性清单
GES目前支持的GQL特性清单如下：
| 章节名                                     | 小节    | 语法名/特性名                              | 关联编号 | 操作示例                                                                                                                                                                                                   |
|:---|:---|:---|:---|:---|
| 9 Procedure specification               | 9.1   | \<next statement\>                   | GQ20 | match (n:user) return n union all match (n:movie) return n next yield n as b match (b)--\>(m) return m                                                                                                 |
| 13 Data-modifying statements(仅持久化版支持)   | 13.2  | \<insert statement\>                 | -    | insert (n:movie{_ID_:'1a', genres: 'Comedy\|Drama'}) return n                                                                                                                                          |
| 13 Data-modifying statements(仅持久化版支持)   | 13.3  | \<set statement\>                    | GD02 | match (n) where element_id(n) = '1a' set n.movieid=1 return n                                                                                                                                          |
| 13 Data-modifying statements(仅持久化版支持)   | 13.4  | \<remove statement\>                 | GD02 | match (n) where element_id(n) = '1a' remove n.movieid return n                                                                                                                                         |
| 13 Data-modifying statements(仅持久化版支持)   | 13.5  | \<delete statement\>                 | -    | match (n) where element_id(n) = '1a' delete n                                                                                                                                                          |
| 14 Query statement                      | 14.2  | union                                | GQ03 | return 1 as a union return 2 as a                                                                                                                                                                      |
| 14 Query statement                      | 14.4  | \<simple match statement\>           | -    | match (n) return n                                                                                                                                                                                     |
| 14 Query statement                      | 14.4  | \<optional match statement\>         | -    | match (n) where id(n)= '1a' optional match （n)--\>(m) return count(\*)                                                                                                                                 |
| 14 Query statement                      | 14.6  | \<filter statement\>                 | GQ08 | match (n) where element_id(n) = '1a' return n                                                                                                                                                          |
| 14 Query statement                      | 14.7  | \<let statement\>                    | GQ09 | let a=1, value b::long=2 return a,b                                                                                                                                                                    |
| 14 Query statement                      | 14.8  | \<for statement\>                    | GQ10 | for a in \[1,2,3\] return a                                                                                                                                                                            |
| 14 Query statement                      | 14.11 | \<return statement\>                 | -    | match (n) return n.name as name, n.age                                                                                                                                                                 |
| 15 Procedure calling                    | 15.3  | \<named procedure call\>             | GP04 | call db.schema()                                                                                                                                                                                       |
| 16 Comment elements                     | 16.4  | \<graph pattern\>                    | G004 | 参见[模式匹配](https://support.huaweicloud.com/api-ges/ges_03_0564.html#ges_03_0564__section1951675271317)章节。                                                                                                |
| 16 Comment elements                     | 16.5  | \<insert graph pattern\>             | -    | insert (n:movie{_ID_:'1a', genres: 'Comedy\|Drama'}) return n                                                                                                                                          |
| 16 Comment elements                     | 16.7  | \<quantified path primary\>          | G036 | match p=(n)-\[r\]-\>{1,3}(m) where element_id(n)= 'xx' return p                                                                                                                                        |
| 16 Comment elements                     | 16.7  | Non-local element pattern predicates | G041 | let a = 'Jaws (1975) ' match (n:movie where n.title=a) return n                                                                                                                                        |
| 16 Comment elements                     | 16.7  | \<full edge pattern\>                | G043 | match (n),(m) where element_id(n)= '100' and element_id(m)= '120' optional match (n)-\[r\]-\>(m) with n,r,m optional match (n)-\[r1\]-(m) with n,r,r1,m optional match (n)\<-\[r2\]-(m) return r,r1,r2 |
| 16 Comment elements                     | 16.8  | \<label expression\>                 | -    | match (n:movie) return count(\*)                                                                                                                                                                       |
| 16 Comment elements                     | 16.8  | \<label disjunction\>                | -    | match (n:movie\|user) return n limit 10                                                                                                                                                                |
| 16 Comment elements                     | 16.8  | \<label negation\>                   | -    | match (n:!movie) return count(\*)                                                                                                                                                                      |
| 16 Comment elements                     | 16.8  | \<parenthesized label expression\>   | -    | match (n:(!movie\&!default)\|user) return count(\*)                                                                                                                                                    |
| 16 Comment elements                     | 16.11 | \<fixed quantifier\>                 | -    | 参见[模式匹配](https://support.huaweicloud.com/api-ges/ges_03_0564.html#ges_03_0564__section1951675271317)章节的"可变长度路径"。                                                                                       |
| 16 Comment elements                     | 16.11 | \<general quantifier\>               | -    | match p=(n)-\[r\]-\>{,3}(m) where element_id(n)= 'xx' return p                                                                                                                                         |
| 16 Comment elements                     | 16.13 | \<where clause\>                     | -    | 参考14.4和14.6                                                                                                                                                                                            |
| 16 Comment elements                     | 16.16 | \<order by clause\>                  | -    | match (n:movie) return n order by n.genres asc                                                                                                                                                         |
| 16 Comment elements                     | 16.18 | \<limit clause\>                     | GQ13 | match (n:movie) return n skip 10 limit 10                                                                                                                                                              |
| 16 Comment elements                     | 16.19 | \<offset clause\>                    | GQ12 | match (n:movie) return n skip 10 limit 10                                                                                                                                                              |
| 19 Predicate                            | 19.3  | \<comparison predicate\>             | -    | let a=1,b=2 return a=b,a\<\>b,a\<b,a\>b,a\<=b,a\>=b                                                                                                                                                    |
| 19 Predicate                            | 19.5  | \<null predicate\>                   | -    | let value a::long=1 return a is null                                                                                                                                                                   |
| 19 Predicate                            | 19.9  | \<label predicate\>                  | G111 | match (n) where element_id(n)= '0' return n:movie                                                                                                                                                      |
| 20 Value expressions and specifications | 20.4  | \<dynamic parameter specification\>  | -    | 参见[Cypher基本操作和兼容性](https://support.huaweicloud.com/api-ges/ges_03_0476.html)和[参数化查询支持](https://support.huaweicloud.com/api-ges/ges_03_0476.html#ges_03_0476__li8383195704410)。                         |
| 20 Value expressions and specifications | 20.7  | \<simple case\>                      | -    | let a =2 return case a when 1 then a+1 else a+2 end                                                                                                                                                    |
| 20 Value expressions and specifications | 20.7  | \<searched case\>                    | -    | let a =2 return case when a=1 then a+1 else a+2 end                                                                                                                                                    |
| 20 Value expressions and specifications | 20.9  | Hrizontal Aggregation                | GE09 | match (n) return labels(n),count(distinct n),avg(n.age), max(n.age),min(n.age),sum(n.age)                                                                                                              |
| 20 Value expressions and specifications | 20.10 | \<element_id function\>              | G100 | match (n) where element_id(n) = '1a' return n                                                                                                                                                          |
| 20 Value expressions and specifications | 20.11 | \<property reference\>               | -    | match (n) where element_id(n) = '1a' return n.movieid                                                                                                                                                  |
| 20 Value expressions and specifications | 20.11 | record property                      | -    | return {name: 'Jay',age:1}.name                                                                                                                                                                        |
| 20 Value expressions and specifications | 20.15 | \<list concatenation\>               | -    | return \[1,2,3,4\]\|\|\[5,6,7,8\]                                                                                                                                                                      |
| 20 Value expressions and specifications | 20.17 | \<list value constructor\>           | -    | return \[1,2,3,4\]                                                                                                                                                                                     |
| 20 Value expressions and specifications | 20.18 | \<record constructor\>               | GV45 | return {name: 'Jay', age:10, details:{salary:1}}                                                                                                                                                       |
| 20 Value expressions and specifications | 20.20 | \<boolean value expression\>         | -    | return (true and false) or false                                                                                                                                                                       |
| 20 Value expressions and specifications | 20.20 | Boolean Xor                          | GE07 | return true xor false                                                                                                                                                                                  |
| 20 Value expressions and specifications | 20.21 | \<numeric value expression\>         | -    | return 1+2,1-2,1\*2,1/2,-2                                                                                                                                                                             |
| 20 Value expressions and specifications | 20.22 | \<char length expression\>           | -    | let value s::STRING = 'hello_world' return character_length(s)                                                                                                                                         |
| 20 Value expressions and specifications | 20.22 | \<path length expression\>           | GF04 | match p=TRAIL (n)--{1,2}(m) where id(n)= '0' return path_length(p)                                                                                                                                     |
| 20 Value expressions and specifications | 20.22 | size function                        | GF13 | let list = \[1,2,3,4\] return size(list)                                                                                                                                                               |
   
#### 支持的GQL可选特性清单
对于可选的GQL特性，GQL标准提供了特性ID和特性名称，目前GES支持的特性如下。
| 特性编号 |                        特性名称                        |
|---|---|
| G004 | Path variables                                     |
| G011 | Advanced path modes: TRAIL                         |
| G036 | Quantified edges                                   |
| G041 | Non-local element pattern predicates               |
| G043 | Complete full edge patterns                        |
| G060 | Bounded graph pattern quantifiers                  |
| G100 | ELEMENT_ID function                                |
| G111 | IS LABELED predicate                               |
| GD01 | Updatable graphs                                   |
| GD02 | Graph label set changes                            |
| GE07 | Boolean XOR                                        |
| GE09 | Horizontal aggregation                             |
| GF01 | Enhanced numeric functions                         |
| GF02 | Trigonometric functions                            |
| GF11 | Advanced aggregate functions: binary set functions |
| GF13 | SIZE function                                      |
| GG02 | Graph with a closed graph type                     |
| GG20 | Explicit element type names                        |
| GP04 | Named procedure calls                              |
| GQ03 | Composite query: UNION                             |
| GQ08 | Filter statement                                   |
| GQ09 | LET statement                                      |
| GQ10 | FOR statement: list value support                  |
| GQ12 | ORDER BY and page statement: OFFSET clause         |
| GQ13 | ORDER BY and page statement: LIMIT clause          |
| GQ20 | Advanced linear composition with NEXT              |
| GV45 | Record types                                       |
| GV47 | Open record type                                   |
| GV48 | Nested record types                                |
| GV50 | List value types                                   |
| GV55 | Path value types                                   |