1、SQL Constraint Integrity Constraints are used to apply business rules for the database tables. The constraints available in SQL are Foreign Key, Not Null, Unique, Check. Constraints can be defined in two ways
drop table parent_zsm_00 cascade constraints; drop table child_zsm_00 cascade constraints; 1.6.4 表中数据的级联删除和级联置空 级联删除:on delete cascade 级联置空:on delete set null /* 创建主表 */ create table parent_zsm_00( id number(7) primary key, name varchar2(25) not null );...
The syntax of the CREATE INDEX, CREATE TABLE, and ALTER TABLE statements supports the keywords ASC (ascending) and DESC (descending) on individual columns in indexes and constraints. Specifying the order in which key values are stored in an index is useful when queries referencing the table ...
数据库对象是数据库的组成部分,常见的有以下几种:表(Table )、索引(Index)、视图(View)、图表(Diagram)、缺省值(Default)、规则(Rule)、触发器(Trigger)、存储过程(Stored Procedure)、 用户(User)等。命名规范是指数据库对象如数据库(SCHEMA)、表(TABLE)、索引(INDEX)、约束(CONSTRAINTS)等的命名约定。 2、数...
The syntax of the CREATE INDEX, CREATE TABLE, and ALTER TABLE statements supports the keywords ASC (ascending) and DESC (descending) on individual columns in indexes and constraints. Specifying the order in which key values are stored in an index is useful when queries referencing the table ...
Can't be created as a constraint-based index. It's possible to have unique constraints, primary key constraints, and foreign key constraints on a table with a columnstore index. Constraints are always enforced with a row-store index. Constraints can't be enforced with a columnstore (clustered...
For more information, see Disable indexes and constraints and Enable indexes and constraints. REORGANIZE a rowstore index For rowstore indexes, REORGANIZE specifies to reorganize the index leaf level. The REORGANIZE operation is: Always performed online. This means long-term blocking table locks aren'...
The syntax of the CREATE INDEX, CREATE TABLE, and ALTER TABLE statements supports the keywords ASC (ascending) and DESC (descending) on individual columns in indexes and constraints.Specifying the order in which key values are stored in an index is useful when queries referencing the table have...
For more information, see Disable indexes and constraints and Enable indexes and constraints. REORGANIZE a rowstore index For rowstore indexes, REORGANIZE specifies to reorganize the index leaf level. The REORGANIZE operation is: Always performed online. This means long-term blocking table locks aren'...
For more information on enabling and using resumableALTER TABLE ADD CONSTRAINToperations, seeResumable add table constraints. MAXDOP =max_degree_of_parallelism Applies to: SQL Server 2008 (10.0.x) and later versions Overrides themax degree of parallelismconfiguration option during the index operation. ...