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。

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           |
...

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：

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            |
+----------------------+---------------+

nebula> GO FROM "player100" OVER follow \
        WHERE $^.player.age >= 42 \
        YIELD dst(edge);
+-------------+
| dst(EDGE)   |
+-------------+
| "player101" |
| "player125" |
+-------------+

过滤边属性：

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           |
...

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¶

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¶

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。

# 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。

# 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。

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。

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。

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。

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。

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¶

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  |
...

最后更新: March 7, 2023

WHERE¶

openCypher 兼容性¶

基础用法¶

用布尔运算符定义条件¶

过滤属性¶

过滤动态计算属性¶

过滤现存属性¶

过滤 rank¶

过滤字符串¶

STARTS WITH¶

ENDS WITH¶

CONTAINS¶

结合 NOT 使用¶

过滤列表¶

匹配列表中的值¶

结合 NOT 使用¶

`STARTS WITH`¶

`ENDS WITH`¶

`CONTAINS`¶