CREATE UNIQUE INDEX for Unique Values If you want to create indexes for unique values in a column, we use theCREATE UNIQUE INDEXconstraint. For example, -- create tableCREATETABLEColleges ( college_idINTPRIMARY
CONSTRAINT PRIMARY KEY [索引类型] (<列名>,…) 在CREATE TABLE 语句中添加此语句,表示在创建新表的同时创建该表的主键。 语法格式: KEY | INDEX [<索引名>] [<索引类型>] (<列名>,…) 在CREATE TABLE 语句中添加此语句,表示在创建新表的同时创建该表的索引。 语法格式: UNIQUE [ INDEX | KEY] [<...
创建索引结构表也是用CREATE TABLE 命令加ORGANIZATION INDEX关键字来实现。但是,这样的表在创建完后,你还必须为该表建立一个主键。 例子: CREATE TABLE IOT_EXPAMPLE ( Pk_col1 number(4), Pk_col2 varchar2(10), Non_pk_col1 varchar2(40), Non_pk_col2 date, CONSTRAINT pk_iot PRIMARY KEY ( pk_...
Create a nonclustered index with a unique constraint and specify the sort order SQL Copy CREATE UNIQUE INDEX index1 ON schema1.table1 (column1 DESC, column2 ASC, column3 DESC); Key scenario: Starting with SQL Server 2016 (13.x), in Azure SQL Database, and in Azure SQL Managed Inst...
CONSTRAINT PRIMARY KEY [索引类型] (<列名>,…) 在CREATE TABLE 语句中添加此语句,表示在创建新表的同时创建该表的主键。 【实例2】创建一个表 tb_stu_info2,在该表的 id 字段上使用 PRIMARY KEY 关键字创建主键索引。 语法格式: KEY | INDEX [<索引名>] [<索引类型>] (<列名>,…) ...
Ordered clustered columnstore indexes were introduced in SQL Server 2022 (16.x). For more information, see CREATE COLUMNSTORE INDEX. For ordered columnstore index availability, see Columnstore indexes: Overview. Starting with SQL Server 2016 (13.x), you can create the table as a clustered columnst...
A unique index, UNIQUE constraint, or PRIMARY KEY constraint cannot be created if duplicate key values exist in the data. A unique nonclustered index can contain included nonkey columns. For more information, see Create an index with included columns....
使用CREATE INDEX 语句创建索引,它允许命名索引,指定表及要索引的一列或多列,并指示索引是升序排列还是降序排列。 索引也可以是唯一的,与 UNIQUE 约束类似,在列上或列组合上防止重复条目。 创建索引 CREATE INDEX CREATE INDEX (创建索引)的语法如下:
You can create a unique constraint in SQL Server by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that don't participate in a primary key. Creating a unique constraint automatically creates a corresponding unique index....
Type the following SQL statement: CREATE INDEX YearIndex ON Cars (Year) On the Design tab, in the Results group, click Run. Top of Page Create a constraint or a relationship A constraint establishes a logical condition that a field or combination of ...