If we want to create indexes for unique values in a column, we use theCREATE UNIQUE INDEXconstraint. For example, -- create unique indexCREATEUNIQUEINDEXcollege_indexONColleges(college_code); Run Code Here, the SQL command creates a unique index namedcollege_indexon theCollegestable using thecol...
可以在创建表时规定约束(通过 CREATE TABLE 语句),或者在表创建之后也可以(通过 ALTER TABLE 语句)。 我们将主要探讨以下几种约束: NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY CHECK DEFAULT SQL NOT NULL 约束 NOT NULL 约束强制列不接受 NULL 值。 SQL UNIQUE 约束 SQL UNIQUE 约束 UNIQUE 约束唯一标识数据库表...
唯一约束 唯一约束可以用两种方式定义:列级唯一约束和表级唯一约束 列级唯一约束演示: create table student( student_id...constraint student_email_uk unique(email) );//表级唯一约束 4.检查约束 检查约束可以用两种方式定义:列级检查约束和表级检查约束 列级检查约束演示: create...,从表关联数据置...
UNIQUE } [ CLUSTERED | NONCLUSTERED ] [ WITH FILLFACTOR = fillfactor | WITH ( <index_option> [ ,... n ] ) ] [ ON { partition_scheme_name ( partition_column_name ) | filegroup | "default" } ] | [ FOREIGN KEY ] REFERENCES referenced_table_name [ ( ref_column ) ] [ ON DELETE...
UNIQUE } [ CLUSTERED | NONCLUSTERED ] [ WITH FILLFACTOR = fillfactor | WITH ( <index_option> [ ,... n ] ) ] [ ON { partition_scheme_name ( partition_column_name ) | filegroup | "default" } ] | [ FOREIGN KEY ] REFERENCES referenced_table_name [ ( ref_column ) ] [ ON DELETE...
[ WITH ] [(]table[)] ] ] ] [WITH table-option ::= { %CLASSPARAMETER paramname [=] value } , } [ STORAGETYPE [=] {ROW | COLUMN} ] ] sqlcollation ::= { %EXACT | %MINUS | %MVR | %PLUS | %SPACE | %SQLSTRING [(maxlen)] | %SQLUPPER [(maxlen)] | %TRUNCATE[(maxlen...
(MAXLEN = 30) [ Required, SqlColumnNumber = 3 ]; Property NAMEFIRST As %Library.String(MAXLEN = 30) [ Required, SqlColumnNumber = 4 ]; Parameter SQLTABLETYPE = "GLOBAL TEMPORARY"; /// DDL Primary Key Specification Index EMPLOYEEPK On EMPNUM [ PrimaryKey, Type = index, Unique ]; ...
(field-commalist)REFERENCEStable[(reffield-commalist)][ONDELETEref-action][ONUPDATEref-action][NOCHECK]}][SHARD[KEY(field-commalist)[COSHARD[WITH][(]table[)]]][WITHtable-option::={%CLASSPARAMETERparamname[=]value},}[STORAGETYPE[=]{ROW|COLUMN}]]sqlcollation::={%EXACT|%MINUS|%MVR|%PLUS...
在以下示例中,使用两种不同的列排序规则创建表MyTable。 默认情况下,列mycolumn1具有默认排序规则Latin1_General_100_CI_AS_KS_WS。 列mycolumn2具有排序规则Frisian_100_CS_AS。 SQL CREATETABLEMyTable ( mycolumnnn1nvarchar, mycolumn2nvarcharCOLLATEFrisian_100_CS_AS )WITH( CLUSTERED COLUMNSTOREINDEX) ;...
createtableDepartment-( --创建部门编号;int代表整数类型;primary key代表主键;identity(1,1)代表从1开始步长为1自增长; DepartmentIdintprimarykeyidentity(1,1), --创建部门名称;nvarchar(50)代表长度50的字符串;not null代表不能为空; DepartmentName nvarchar(50)notnull, ...