Constraints on a table in Oracle can be found using the below views user_constraints: It provides information about constraints owned by the current user. all_constraints:shows information about constraints accessible to the current user, including those owned by other users. dba_constraints: provides...
status--是否启用 from user_constraints--[all_constraints|dba_constraints] where constraint_name='CHECK_TB_SUPPLIER_ID'; 8. 删除CHECK约束 8.1 语法 ALTER TABLE table_name DROP CONSTRAINT constraint_name; 8.2 演示样例 ALTER TABLE tb_supplier DROP CONSTRAINT check_tb_supplier_id; --- 假设您们在尝...
Constraints have names. It is good practice to specify the names with a standard naming convention, but if they are not explicitly named, Oracle will generate names. 由上可知,每一个约束都有名称,最好的做法是在定义约束是显式的命名,如果没有显式命名,那么系统会提供一个名字。 Check Constraints A...
当表已被创建时,如需在 "P_Id" 列创建 CHECK 约束,请使用下面的 SQL: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons ADD CHECK (P_Id>0) 如需命名 CHECK 约束,并定义多个列的 CHECK 约束,请使用下面的 SQL 语法: MySQL / SQL Server / Oracle / MS Access: ALTER TABLE Persons...
可以在CHECK条件中使用任意有效的SQL表达式，CHECK约束对于插入、更新等任何对数据进行变化的操作都进行检查...
关于Oracle Check类型约束的导入与启用 今天有朋友问,Oracle的Check约束在indexfile中是否存在,导入后没有检查到。 我测试了一下,事实证明是可以的,Oracle的Check Constraints可以通过imp,使用indexfile来获得,并且可以通过手工执行脚本来加载。 以下是一个简单的测试过程。创建测试表:...
It is not good practice to have a constraint defined like that based on a particular value in another column. I asked him to explain but he would not. Could someone explain as to why something like this is frowned upon? And if it indeed is not good practice, then ...
SQL 型 V4.3.5 参考指南 系统视图 MySQL 租户系统视图 字典视图 information_schema.CHECK_CONSTRAINTS 更新时间:2025-01-30 23:00:01 编辑 功能 记录了CREATE TABLE操作时,有关表和列相关的约束信息。 说明 从V3.2.3 版本开始引入。 字段说明 字段名称类型是否可以为 NULL描述 ...
It's a good practice to createnamed constraintsso that it is easier to alter and drop constraints. Here's an example to create a namedCHECKconstraint: -- create a named constraint named amountCK-- the constraint makes sure that amount is greater than 0CREATETABLEOrders ( ...
types of constraints (primary key, unique index, foreign key, check) belong to the same namespace. In MySQL, each constraint type hasits own namespace per schema (database). Consequently, CHECK constraint namesmust be unique per schema; no two tables in the same schema can share a CHECK...