Summary: in this tutorial, you will learn about the PostgreSQL foreign key and how to add foreign keys to tables using foreign key constraints. Introduction to PostgreSQL Foreign Key Constraint In PostgreSQL, a
Primary Keys Constraint: both unique and not null. A table can only hasONEprimary key, although this primary key can be a group of columns (a composition primary key). Foreign Keys Constraint: specifies that values in a column (or group of columns) must match the values appearing in some ...
确保某列(或两个列多个列的结合)有唯一标识,有助于更容易更快速地找到表中的一个特定的记录。 FOREIGN Key: 保证一个表中的数据匹配另一个表中的值的参照完整性。 CHECK: 保证列中的值符合指定的条件。 EXCLUSION:排他约束,保证如果将任何两行的指定列或表达式使用指定操作符进行比较,至少其中一个操作符比较将...
除非cascade_via_foreign_keys自變數設定為 true,否則適用於 PostgreSQL 的 Azure Cosmos DB 不會取消散發具有或由外鍵參考的數據表。 如果這個自變數為 false(或省略),則您必須在取消散發之前手動卸除違規的外鍵條件約束。 引數 table_name: 未散發的分散式或參考數據表名稱。 cascade_via_foreign_keys: (選擇性...
-- Foreign Keys structure for table inet_workbench_widget -- --- ALTER TABLE "public"."inet_workbench_widget" ADD CONSTRAINT "fk1iog8qeh9355qo1lbuyx4yuh2" FOREIGN KEY ("dashboard_id") REFERENCES "public"."inet_workbench_dashboard" ("id") ON DELETE NO ACTION ON UPDATE NO ACTION; ...
List of fixed system views are sys.check_constraints, sys.data_spaces, sys.default_constraints, sys.dm_exec_connections, sys.foreign_keys, sys.key_constraints, sys.stats, sys.syscolumns, sys.sysforeignkeys, sys.sysprocesses, sys.system_objects, sys.table_types, sys.tables, sys.types, sys....
Foreign keys can make it difficult to sync data. Three options are: Defer constraints (recommended) Manually specify the order of tables Disable foreign key triggers, which can silently break referential integrity (not recommended) To defer constraints, use: ...
createkeys.sql脚本生成另一个名为addkeys.sql的SQL 脚本,该脚本将重新创建所有外键。 迁移数据库后,将运行 addkeys.sql 脚本: Bash 复制 psql -h adventureworks[nnn].postgres.database.azure.com -U azureuser@adventureworks[nnn] -d azureadventureworks -f workshop/migration_sampl...
Table partitioning (range and list partitioning) Tablespaces Constraints Unique Foreign key Primary key Check constraints Exclusion constraints Unique, primary key, and foreign key constraints are permitted, but they are informational only. They are not enforced by the system, but they are used by the...
CREATE TABLE device_types ( device_type_id int primary key, device_type_name text not null unique ); -- replicate the table across all nodes to enable foreign keys and joins on any column SELECT create_reference_table('device_types'); -- insert a device type INSERT INTO device_types (...