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_idINTPRIMARYKEY, college_codeVARCHAR(20)NOTNULL, college_nameVARCHAR(50) );-- create unique in...
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_...
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] [<...
Notice that none of the rows from the Production.UnitMeasure table were inserted into the table even though only one row in the table violated the UNIQUE index constraint. E. Using DROP_EXISTING to drop and re-create an index The following example drops and re-creates an existing index on ...
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>,…) ...
-- Create a nonclustered index with a unique constraint -- on 3 columns and specify the sort order for each column CREATE UNIQUE INDEX index1 ON schema1.table1 (column1 DESC, column2 ASC, column3 DESC); 主要方案: 从SQL Server 2016 (13.x) 和 SQL 数据库 开始,针对列存储索引使用非聚集...
A key definition includes the Unique property that you can use to create a unique constraint on the table in SQL Server. A unique key ensures that records in a table don't have identical field values. With a unique key, when table is validated, the key value is checked for uniqueness. ...
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....
The result is that the index constraint is violated only if promotion_id is equal to 2 for two rows with the same customer_id value. Partitioned Index ExamplesCreating a Range-Partitioned Global Index: ExampleThe following statement creates a global prefixed index cost_ix on the sample table...
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: