📅 最后修改于: 2020-11-27 06:49:28 🧑 作者: Mango
CQL代表Cypher Query Language。就像Oracle数据库具有查询语言SQL一样，Neo4j也具有CQL作为查询语言。
Neo4j CQL具有执行数据库操作的命令。
Neo4j CQL支持许多子句，例如WHERE，ORDER BY等，以轻松的方式编写非常复杂的查询。
Neo4j CQL支持某些功能，例如字符串，聚合。除了它们，它还支持一些关系函数。
以下是Neo4j的Çypher Q uery大号anguage的阅读条款-
| Sr.No | Read Clauses | Usage |
|---|---|---|
| 1 | MATCH | This clause is used to search the data with a specified pattern. |
| 2 | OPTIONAL MATCH | This is the same as match, the only difference being it can use nulls in case of missing parts of the pattern. |
| 3 | WHERE | This clause id is used to add contents to the CQL queries. |
| 4 | START | This clause is used to find the starting points through the legacy indexes. |
| 5 | LOAD CSV | This clause is used to import data from CSV files. |
以下是Neo4j的Çypher Q uery大号anguage的写入条款-
| Sr.No | Write Clause | Usage |
|---|---|---|
| 1 | CREATE | This clause is used to create nodes, relationships, and properties. |
| 2 | MERGE | This clause verifies whether the specified pattern exists in the graph. If not, it creates the pattern. |
| 3 | SET | This clause is used to update labels on nodes, properties on nodes and relationships. |
| 4 | DELETE | This clause is used to delete nodes and relationships or paths etc. from the graph. |
| 5 | REMOVE | This clause is used to remove properties and elements from nodes and relationships. |
| 6 | FOREACH | This class is used to update the data within a list. |
| 7 | CREATE UNIQUE | Using the clauses CREATE and MATCH, you can get a unique pattern by matching the existing pattern and creating the missing one. |
| 8 | Importing CSV files with Cypher | Using Load CSV you can import data from .csv files. |
以下是Neo4j的Çypher Q uery大号anguage的一般条款-
| Sr.No | General Clauses | Usage |
|---|---|---|
| 1 | RETURN | This clause is used to define what to include in the query result set. |
| 2 | ORDER BY | This clause is used to arrange the output of a query in order. It is used along with the clauses RETURN or WITH. |
| 3 | LIMIT | This clause is used to limit the rows in the result to a specific value. |
| 4 | SKIP | This clause is used to define from which row to start including the rows in the output. |
| 5 | WITH | This clause is used to chain the query parts together. |
| 6 | UNWIND | This clause is used to expand a list into a sequence of rows. |
| 7 | UNION | This clause is used to combine the result of multiple queries. |
| 8 | CALL | This clause is used to invoke a procedure deployed in the database. |
以下是常用的Neo4j CQL函数-
| Sr.No | CQL Functions | Usage |
|---|---|---|
| 1 | String | They are used to work with String literals. |
| 2 | Aggregation | They are used to perform some aggregation operations on CQL Query results. |
| 3 | Relationship | They are used to get details of relationships such as startnode, endnode, etc. |
我们将在后续章节中详细讨论所有Neo4j CQL命令，子句和函数的语法，用法和示例。
这些数据类型类似于Java语言。它们用于定义节点或关系的属性。
Neo4j CQL支持以下数据类型-
| Sr.No | CQL Data Type | Usage |
|---|---|---|
| 1 | Boolean | It is used to represent Boolean literals: true, false. |
| 2 | byte | It is used to represent 8-bit integers. |
| 3 | short | It is used to represent 16-bit integers. |
| 4 | int | It is used to represent 32-bit integers. |
| 5 | long | It is used to represent 64-bit integers. |
| 6 | float | It is used to represent 32-bit floating-point numbers. |
| 7 | double | It is used to represent 64-bit floating-point numbers. |
| 8 | char | It is used to represent 16-bit characters. |
| 9 | String | It is used to represent Strings. |
以下是Neo4j Cypher Query语言支持的运算符列表。
| Sr.No | Type | Operators |
|---|---|---|
| 1 | Mathematical | +, -, *, /, %, ^ |
| 2 | Comparison | +, <>, <, >, <=, >= |
| 3 | Boolean | AND, OR, XOR, NOT |
| 4 | String | + |
| 5 | List | +, IN, [X], [X…..Y] |
| 6 | Regular Expression | =- |
| 7 | String matching | STARTS WITH, ENDS WITH, CONSTRAINTS |
Neo4j支持以下布尔运算符，以在Neo4j CQL WHERE子句中使用以支持多个条件。
| Sr.No | Boolean Operators | Description |
|---|---|---|
| 1 | AND | It is a Neo4j CQL keyword to support AND operation. It is like SQL AND operator. |
| 2 | OR | It is a Neo4j CQL keyword to support OR operation. It is like SQL AND operator. |
| 3 | NOT | It is a Neo4j CQL keyword to support NOT operation. It is like SQL AND operator. |
| 4 | XOR | It is a Neo4j CQL keyword to support XOR operation. It is like SQL AND operator. |
的Neo4j支持以下运算符中的Neo4j CQL使用WHERE子句来支持的条件。
| Sr.No | Boolean Operators | Description |
|---|---|---|
| 1 | = | It is a Neo4j CQL “Equal To” operator. |
| 2 | < > | It is a Neo4j CQL “Not Equal To” operator. |
| 3 | < | It is a Neo4j CQL “Less Than” operator. |
| 4 | > | It is a Neo4j CQL “Greater Than” operator. |
| 5 | <= | It is a Neo4j CQL “Less Than Or Equal To” operator. |
| 6 | > = | It is a Neo4j CQL “Greater Than Or Equal To” operator. |