Union

本页描述如何使用 Cypher®.Union 类创建 UNION 子句。

通过向 Cypher.Union 类传入多个子句来创建多个查询的并集。请注意，所有子句必须是不同的实例，因为 Cypher Builder 子句不能重复使用。

const returnVar = new Cypher.Variable();
const n1 = new Cypher.Node();
const query1 = new Cypher.Match(new Cypher.Pattern(n1, { labels: ["Movie"] })).return([n1, returnVar]);
const n2 = new Cypher.Node();
const query2 = new Cypher.Match(new Cypher.Pattern(n2, { labels: ["Movie"] })).return([n2, returnVar]);
const n3 = new Cypher.Node();
const query3 = new Cypher.Match(new Cypher.Pattern(n3, { labels: ["Movie"] })).return([n3, returnVar]);

const unionQuery = new Cypher.Union(query1, query2, query3);

这将生成以下 UNION 子句

MATCH (this0:Movie)
RETURN this0 AS var1
UNION
MATCH (this2:Movie)
RETURN this2 AS var1
UNION
MATCH (this3:Movie)
RETURN this3 AS var1

请注意，此示例使用额外变量 returnVar，以确保所有查询返回相同的变量名称。

UNION ALL

UNION 默认会去除重复项。若要保留全部结果，请使用 .all() 方法来创建 UNION ALL 子句。

const returnVar = new Cypher.Variable();
const n1 = new Cypher.Node();
const query1 = new Cypher.Match(new Cypher.Pattern(n1, { labels: ["Movie"] })).return([n1, returnVar]);
const n2 = new Cypher.Node();
const query2 = new Cypher.Match(new Cypher.Pattern(n2, { labels: ["Movie"] })).return([n2, returnVar]);
const n3 = new Cypher.Node();
const query3 = new Cypher.Match(new Cypher.Pattern(n3, { labels: ["Movie"] })).return([n3, returnVar]);

const unionQuery = new Cypher.Union(query1, query2, query3).all();

这将生成以下 UNION 子句

MATCH (this0:Movie)
RETURN this0 AS var1
UNION ALL
MATCH (this2:Movie)
RETURN this2 AS var1
UNION ALL
MATCH (this3:Movie)
RETURN this3 AS var1