WHERE¶
WHERE子句可以根据条件过滤输出结果。
WHERE子句通常用于如下查询：
- 原生 nGQL，例如
GO和LOOKUP语句。
- openCypher 方式，例如
MATCH和WITH语句。
openCypher 兼容性¶
- 不支持在
WHERE子句中使用 Pattern（TODO: planning），例如WHERE (v)-->(v2)。
- 过滤 Rank 是原生 nGQL 功能。如需在 openCypher 兼容语句中直接获取 Rank 值，可以使用 rank() 函数，例如
MATCH (:player)-[e:follow]->() RETURN rank(e);。
基础用法¶
Note
下文示例中的$$、$^等是引用符号，详情请参见引用符。
用布尔运算符定义条件¶
在WHERE子句中使用布尔运算符NOT、AND、OR和XOR定义条件。关于运算符的优先级，请参见运算符优先级。
ngql
nebula> MATCH (v:player) \
WHERE v.player.name == "Tim Duncan" \
XOR (v.player.age < 30 AND v.player.name == "Yao Ming") \
OR NOT (v.player.name == "Yao Ming" OR v.player.name == "Tim Duncan") \
RETURN v.player.name, v.player.age;
+-------------------------+--------------+
| v.player.name | v.player.age |
+-------------------------+--------------+
| "Danny Green" | 31 |
| "Tiago Splitter" | 34 |
| "David West" | 38 |
...
ngql
nebula> GO FROM "player100" \
OVER follow \
WHERE properties(edge).degree > 90 \
OR properties($$).age != 33 \
AND properties($$).name != "Tony Parker" \
YIELD properties($$);
+----------------------------------+
| properties($$) |
+----------------------------------+
| {age: 41, name: "Manu Ginobili"} |
+----------------------------------+
过滤属性¶
在WHERE子句中使用点或边的属性定义条件。
- 过滤点属性：
ngql nebula> MATCH (v:player)-[e]->(v2) \ WHERE v2.player.age < 25 \ RETURN v2.player.name, v2.player.age; +----------------------+---------------+ | v2.player.name | v2.player.age | +----------------------+---------------+ | "Ben Simmons" | 22 | | "Luka Doncic" | 20 | | "Kristaps Porzingis" | 23 | +----------------------+---------------+ngql nebula> GO FROM "player100" OVER follow \ WHERE $^.player.age >= 42 \ YIELD dst(edge); +-------------+ | dst(EDGE) | +-------------+ | "player101" | | "player125" | +-------------+
- 过滤边属性：
ngql nebula> MATCH (v:player)-[e]->() \ WHERE e.start_year < 2000 \ RETURN DISTINCT v.player.name, v.player.age; +--------------------+--------------+ | v.player.name | v.player.age | +--------------------+--------------+ | "Tony Parker" | 36 | | "Tim Duncan" | 42 | | "Grant Hill" | 46 | ...ngql nebula> GO FROM "player100" OVER follow \ WHERE follow.degree > 90 \ YIELD dst(edge); +-------------+ | dst(EDGE) | +-------------+ | "player101" | | "player125" | +-------------+
过滤动态计算属性¶
ngql
nebula> MATCH (v:player) \
WHERE v[toLower("AGE")] < 21 \
RETURN v.player.name, v.player.age;
+---------------+-------+
| v.name | v.age |
+---------------+-------+
| "Luka Doncic" | 20 |
+---------------+-------+
过滤现存属性¶
ngql
nebula> MATCH (v:player) \
WHERE exists(v.player.age) \
RETURN v.player.name, v.player.age;
+-------------------------+--------------+
| v.player.name | v.player.age |
+-------------------------+--------------+
| "Danny Green" | 31 |
| "Tiago Splitter" | 34 |
| "David West" | 38 |
...
过滤 rank¶
在 nGQL 中，如果多个边拥有相同的起始点、目的点和属性，则它们的唯一区别是 rank 值。在WHERE子句中可以使用 rank 过滤边。
```ngql
创建测试数据。¶
nebula> CREATE SPACE IF NOT EXISTS test (vid_type=FIXED_STRING(30)); nebula> USE test; nebula> CREATE EDGE IF NOT EXISTS e1(p1 int); nebula> CREATE TAG IF NOT EXISTS person(p1 int); nebula> INSERT VERTEX person(p1) VALUES "1":(1); nebula> INSERT VERTEX person(p1) VALUES "2":(2); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@0:(10); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@1:(11); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@2:(12); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@3:(13); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@4:(14); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@5:(15); nebula> INSERT EDGE e1(p1) VALUES "1"->"2"@6:(16);
通过 rank 过滤边，查找 rank 大于 2 的边。¶
nebula> GO FROM "1" \ OVER e1 \ WHERE rank(edge) > 2 \ YIELD src(edge), dst(edge), rank(edge) AS Rank, properties(edge).p1 | \ ORDER BY $-.Rank DESC; +-----------+-----------+------+---------------------+ | src(EDGE) | dst(EDGE) | Rank | properties(EDGE).p1 | +-----------+-----------+------+---------------------+ | "1" | "2" | 6 | 16 | | "1" | "2" | 5 | 15 | | "1" | "2" | 4 | 14 | | "1" | "2" | 3 | 13 | +-----------+-----------+------+---------------------+ ```
过滤字符串¶
在WHERE子句中使用STARTS WITH、ENDS WITH或CONTAINS可以匹配字符串的特定部分。匹配时区分大小写。
STARTS WITH¶
STARTS WITH会从字符串的起始位置开始匹配。
```ngql
查询姓名以 T 开头的 player 信息。¶
nebula> MATCH (v:player) \ WHERE v.player.name STARTS WITH "T" \ RETURN v.player.name, v.player.age; +------------------+--------------+ | v.player.name | v.player.age | +------------------+--------------+ | "Tony Parker" | 36 | | "Tiago Splitter" | 34 | | "Tim Duncan" | 42 | | "Tracy McGrady" | 39 | +------------------+--------------+ ```
如果使用小写t（STARTS WITH "t"），会返回空集，因为数据库中没有以小写t开头的姓名。
ngql
nebula> MATCH (v:player) \
WHERE v.player.name STARTS WITH "t" \
RETURN v.player.name, v.player.age;
Empty set (time spent 5080/6474 us)
ENDS WITH¶
ENDS WITH会从字符串的结束位置开始匹配。
ngql
nebula> MATCH (v:player) \
WHERE v.player.name ENDS WITH "r" \
RETURN v.player.name, v.player.age;
+------------------+--------------+
| v.player.name | v.player.age |
+------------------+--------------+
| "Tony Parker" | 36 |
| "Tiago Splitter" | 34 |
| "Vince Carter" | 42 |
+------------------+--------------+
CONTAINS¶
CONTAINS会检查关键字是否匹配字符串的某一部分。
ngql
nebula> MATCH (v:player) \
WHERE v.player.name CONTAINS "Pa" \
RETURN v.player.name, v.player.age;
+---------------+--------------+
| v.player.name | v.player.age |
+---------------+--------------+
| "Paul George" | 28 |
| "Tony Parker" | 36 |
| "Paul Gasol" | 38 |
| "Chris Paul" | 33 |
+---------------+--------------+
结合 NOT 使用¶
用户可以结合布尔运算符NOT一起使用，否定字符串匹配条件。
ngql
nebula> MATCH (v:player) \
WHERE NOT v.player.name ENDS WITH "R" \
RETURN v.player.name, v.player.age;
+-------------------------+--------------+
| v.player.name | v.player.age |
+-------------------------+--------------+
| "Danny Green" | 31 |
| "Tiago Splitter" | 34 |
| "David West" | 38 |
| "Russell Westbrook" | 30 |
...
过滤列表¶
匹配列表中的值¶
使用IN运算符检查某个值是否在指定列表中。
```ngql nebula> MATCH (v:player) \ WHERE v.player.age IN range(20,25) \ RETURN v.player.name, v.player.age; +-------------------------+--------------+ | v.player.name | v.player.age | +-------------------------+--------------+ | "Ben Simmons" | 22 | | "Giannis Antetokounmpo" | 24 | | "Kyle Anderson" | 25 | | "Joel Embiid" | 25 | | "Kristaps Porzingis" | 23 | | "Luka Doncic" | 20 | +-------------------------+--------------+
nebula> LOOKUP ON player \ WHERE player.age IN [25,28] \ YIELD properties(vertex).name, properties(vertex).age; +-------------------------+------------------------+ | properties(VERTEX).name | properties(VERTEX).age | +-------------------------+------------------------+ | "Kyle Anderson" | 25 | | "Damian Lillard" | 28 | | "Joel Embiid" | 25 | | "Paul George" | 28 | | "Ricky Rubio" | 28 | +-------------------------+------------------------+ ```
结合 NOT 使用¶
ngql
nebula> MATCH (v:player) \
WHERE v.player.age NOT IN range(20,25) \
RETURN v.player.name AS Name, v.player.age AS Age \
ORDER BY Age;
+---------------------+-----+
| Name | Age |
+---------------------+-----+
| "Kyrie Irving" | 26 |
| "Cory Joseph" | 27 |
| "Damian Lillard" | 28 |
| "Paul George" | 28 |
| "Ricky Rubio" | 28 |
...