UNIQUE(ID) ); To name aUNIQUEconstraint, and to define aUNIQUEconstraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: CREATETABLEPersons ( ID intNOTNULL, LastName varchar(255)NOTNULL,
The UNIQUE constraint uniquely identifies each record in a database table. The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns. A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it. Note that you can have many UNI...
Here, the SQL command adds theUNIQUEconstraint to thecolleges_idcolumn in the existingCollegestable. For Multiple Columns -- add unique constraint to multiple columnsALTERTABLECollegesADDUNIQUEUnique_College (college_id, college_code); Here, the SQL command adds theUNIQUEconstraint tocollege_idandcoll...
启动tomcat--./startup.sh 然后访问http://localhost:8080 和 http://localhost:9080 都可以看到熟悉...
1 pip3 install sqlalchemy 组成部分： Engine，框架的引擎 Connection Pooling ，数据库...
alter table student add constraint fk_student_ID foreign key(ID) references achievement(ID); 1. 如图: 注意,科普一下:外键不一定要是另一个表的主键(primary key:主键约束),也可以是另一个表的唯一值(unique:唯一约束)。 因为外键和另一张表所关联的字段,值是不能重复(而主键约束是一行数据的唯一标识,...
constraint primary key clustered, --主键 --1 创建外键 int not null constraint foreign key references tbDept(dId), char(18) not null constraint UQ_UserCIP_MyUserInfo unique,--唯一约束 char(6) not null constraint UQ_userJSID_MyUserId unique,--唯一约束 ...
--The unique constraint is preserved as a nonclustered index on the columnstore table. CREATE CLUSTERED COLUMNSTORE INDEX t_account_cci ON t_account --By using the previous two steps, every row in the table meets the UNIQUE constraint --on a non-NULL column. --This has the same end-...
Microsoft.SqlServer.Management.SqlParser.SqlCodeDom.SqlUniqueConstraint Implements ISqlTableElement Properties BoundObject(Inherited fromSqlCodeObject) Children ClusterOption EndLocation(Inherited fromSqlCodeObject) IndexedColumns IndexOptions IsSqlCodeSnippet(Inherited fromSqlCodeObject) ...
Microsoft SQL Server 将保留关键字用于定义、操作和访问数据库。保留关键字是 SQL Server 使用的 Transact-SQL 语言语法的一部分,用于分析和理解 Transact-SQL 语句和批处理。尽管在 Transact-SQL 脚本中使用 SQL Server 保留关键字作为标识符和对象名在语法上是可行的,但规定只能使用分隔标识符。