约束管理 #

约束作用：
├── 保证数据唯一性
├── 保证数据存在性
├── 保证数据完整性
├── 防止无效数据
└── 维护数据质量

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.id IS UNIQUE

CREATE CONSTRAINT person_id_unique FOR (p:Person) REQUIRE p.id IS UNIQUE

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.email IS UNIQUE

CREATE (p:Person {email: 'tom@example.com'})
CREATE (p:Person {email: 'tom@example.com'})

SHOW CONSTRAINTS

DROP CONSTRAINT person_id_unique

CREATE CONSTRAINT FOR (p:Person) REQUIRE (p.firstName, p.lastName) IS NODE KEY

CREATE CONSTRAINT person_name_key FOR (p:Person) REQUIRE (p.firstName, p.lastName) IS NODE KEY

CREATE CONSTRAINT FOR (p:Person) REQUIRE (p.firstName, p.lastName) IS NODE KEY

CREATE (p:Person {firstName: 'Tom', lastName: 'Hanks'})
CREATE (p:Person {firstName: 'Tom', lastName: 'Hanks'})

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.name IS NOT NULL

CREATE CONSTRAINT person_name_exists FOR (p:Person) REQUIRE p.name IS NOT NULL

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.name IS NOT NULL

CREATE (p:Person {name: 'Tom'})
CREATE (p:Person {age: 30})

DROP CONSTRAINT person_name_exists

CREATE CONSTRAINT FOR ()-[r:KNOWS]-() REQUIRE r.id IS UNIQUE

CREATE CONSTRAINT FOR ()-[r:KNOWS]-() REQUIRE r.since IS NOT NULL

CREATE CONSTRAINT FOR ()-[r:KNOWS]-() REQUIRE (r.from, r.to) IS RELATIONSHIP KEY

SHOW CONSTRAINTS

SHOW CONSTRAINTS WHERE name = 'person_id_unique'

SHOW CONSTRAINTS YIELD name, type, entityType, labelsOrTypes, properties

SHOW CONSTRAINTS WHERE type = 'UNIQUENESS'
SHOW CONSTRAINTS WHERE type = 'NODE_KEY'
SHOW CONSTRAINTS WHERE type = 'NODE_PROPERTY_EXISTENCE'

DROP CONSTRAINT person_id_unique

DROP CONSTRAINT IF EXISTS person_id_unique

CALL apoc.schema.assert({}, {})

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.id IS UNIQUE

SHOW INDEXES WHERE owningConstraint IS NOT NULL

DROP CONSTRAINT person_id_unique

CREATE CONSTRAINT FOR (u:User) REQUIRE u.id IS UNIQUE
CREATE CONSTRAINT FOR (u:User) REQUIRE u.email IS UNIQUE

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.name IS NOT NULL
CREATE CONSTRAINT FOR (o:Order) REQUIRE o.createdAt IS NOT NULL

CREATE CONSTRAINT FOR (p:Person) REQUIRE (p.firstName, p.lastName, p.birthDate) IS NODE KEY

命名建议：
├── 使用描述性名称
├── 包含标签名
├── 包含属性名
├── 包含约束类型
└── 使用下划线分隔

建议：
├── 每个标签至少有一个唯一约束
├── 避免过多的存在约束
├── 合理使用节点键约束
└── 定期审查约束

影响：
├── 插入时需要检查约束
├── 更新时需要检查约束
├── 批量导入时影响较大
└── 建议导入后创建约束

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.id IS UNIQUE

MATCH (p:Person)
WHERE p.id = 'person_001'
RETURN p

CALL {
    LOAD CSV WITH HEADERS FROM 'file:///data.csv' AS row
    CREATE (p:Person {id: row.id, name: row.name})
} IN TRANSACTIONS OF 1000 ROWS

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.id IS UNIQUE

CREATE CONSTRAINT user_id_unique FOR (u:User) REQUIRE u.id IS UNIQUE
CREATE CONSTRAINT user_email_unique FOR (u:User) REQUIRE u.email IS UNIQUE
CREATE CONSTRAINT user_username_unique FOR (u:User) REQUIRE u.username IS UNIQUE
CREATE CONSTRAINT user_name_exists FOR (u:User) REQUIRE u.name IS NOT NULL

CREATE CONSTRAINT product_id_unique FOR (p:Product) REQUIRE p.id IS UNIQUE
CREATE CONSTRAINT product_sku_unique FOR (p:Product) REQUIRE p.sku IS UNIQUE
CREATE CONSTRAINT product_name_exists FOR (p:Product) REQUIRE p.name IS NOT NULL
CREATE CONSTRAINT product_price_exists FOR (p:Product) REQUIRE p.price IS NOT NULL

CREATE CONSTRAINT order_id_unique FOR (o:Order) REQUIRE o.id IS UNIQUE
CREATE CONSTRAINT order_number_unique FOR (o:Order) REQUIRE o.orderNumber IS UNIQUE
CREATE CONSTRAINT order_status_exists FOR (o:Order) REQUIRE o.status IS NOT NULL
CREATE CONSTRAINT order_created_exists FOR (o:Order) REQUIRE o.createdAt IS NOT NULL

CREATE CONSTRAINT knows_since_exists FOR ()-[r:KNOWS]-() REQUIRE r.since IS NOT NULL
CREATE CONSTRAINT purchased_at_exists FOR ()-[r:PURCHASED]-() REQUIRE r.purchasedAt IS NOT NULL

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.email IS UNIQUE

CREATE (p:Person {email: 'tom@example.com'})
CREATE (p:Person {email: 'tom@example.com'})

MERGE (p:Person {email: 'tom@example.com'})
ON CREATE SET p.name = 'Tom'

CREATE CONSTRAINT FOR (p:Person) REQUIRE p.name IS NOT NULL

CREATE (p:Person {age: 30})

CREATE (p:Person {name: 'Tom', age: 30})

CALL apoc.do.when(
    EXISTS((:Person {email: 'tom@example.com'})),
    'RETURN "Email already exists" AS message',
    'CREATE (p:Person {email: "tom@example.com"}) RETURN p',
    {}
) YIELD value
RETURN value