Unique constraints and check constraints Create Modify Delete Check constraints Temporal tables Tutorials Reference Track changes Triggers User-defined functions Views XML data Development Internals & architecture Installation Migrate & load data Manage, monitor, & tune ...
altertablePersonsaddunique(id_p);altertablePersonsadd constraintuc_PersonIDunique(id_p, lastname); 2)PRIMARY KEY(两种写法) --注:如果使用ALTER TABLE语句添加主键,必须把主键列声明为不包含NULL值(在表首次创建时)。 altertablePersonsaddprimarykey(id_p);altertablePersonsadd constraintuc_PersonIDprimaryke...
在使用索引创建向导创建索引时,不能将计算列包含在索引中,但在直接创建或使用CREATE INDEX命令创建索引时,则可以对计算机列创建索引,这在SQL Server2000以前的版本中是不允许的,算得上是一大改进。 例8-1: 为表products 创建一个簇索引。 create unique clustered index pk_p_id on products(p_id) with pad_i...
key_name Specifies the unique name by which the symmetric key is known in the database. This is a required parameter. Temporary keys are designated when thekey_namebegins with one number (#) sign. For example,#temporaryKey900007. You can't create a symmetric key that has a name that sta...
Applies to: SQL Server Azure SQL Database Azure SQL Managed InstanceThis topic describes how to create a unique index on a table in SQL Server by using SQL Server Management Studio or Transact-SQL. A unique index guarantees that the index key contains no duplicate values and therefore every ...
key_name Specifies the unique name by which the symmetric key is known in the database. This is a required parameter. Temporary keys are designated when thekey_namebegins with one number (#) sign. For example,#temporaryKey900007. You can't create a symmetric key that has a name that sta...
To create a unique index on a table, using: SQL Server Management Studio Transact-SQL Before You Begin Benefits of a Unique Index Multicolumn unique indexes guarantee that each combination of values in the index key is unique. For example, if a unique index is created on a combination ofLas...
5:unique约束 unique约束与主键约束类似,同样也是要求指定的列有唯一的值 但是一个表中可以有多个unique约束的列,同时这个列允许存在null值。(最多有一个null值) 看例子: create table shippers ( id int indentity not null primery key, zip varchar(10) not null , ...
SQL Server、Azure SQL Database、Azure SQL 受控執行個體的語法syntaxsql 複製 CREATE [ UNIQUE ] [ CLUSTERED | NONCLUSTERED ] INDEX index_name ON ( column [ ASC | DESC ] [ ,...n ] ) [ INCLUDE ( column_name [ ,...n ] ) ] [ WHERE <filter_predicate> ] [ WITH ( <relational...
To create a unique index on a table, using: SQL Server Management Studio Transact-SQL Before You Begin Benefits of a Unique Index Multicolumn unique indexes guarantee that each combination of values in the index key is unique. For example, if a unique index is created on a combination ofLas...