For Multiple Columns -- add unique constraint to multiple columnsALTERTABLECollegesADDUNIQUEUnique_College (college_id, college_code); Here, the SQL command adds theUNIQUEconstraint tocollege_idandcollege_codecolumns in the existingCollegestable. Also,Unique_Collegeis a name given to theUNIQUEconstrain...
To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple columns, use the following SQL syntax: MySQL / SQL Server / Oracle / MS Access: ALTERTABLEPersonsADDCONSTRAINTuc_PersonIDUNIQUE(P_Id,LastName) To DROP a UNIQUE Constraint To drop a UNIQUE constraint, us...
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,
@Cacheable使用两个或多个参数作为缓存的key 常见的如分页查询：使用单引号指定分割符，最终会拼接为一...
constraint UQ_userJSID_MyUserId unique,--唯一约束 varchar(20) not null, varchar(12) null, int null, int not null --用户年龄在2-120岁之间 constraint CHK_UserAge_MyUserInfo check(UserAge >2 && UserAge <120) char(2) not null --用户性别男或女 ...
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,...
报错:Update row with Key (id)=(xxxx) multiple times或者duplicate key value violates unique constraint 问题原因:违反唯一性约束,执行UPDATE、INSERT ON CONFLICT或INSERT操作时,主键存在重复数据。 解决方法: 若INSERT语法报错:可以改为INSERT INTO xx ON CONFLICT的语法,实现主键去重,详情请参见INSERT ON CONFLIC...
Microsoft.SqlServer.Management.SqlParser.SqlCodeDom.SqlUniqueConstraint Implements ISqlTableElement Properties BoundObject(Inherited fromSqlCodeObject) Children ClusterOption EndLocation(Inherited fromSqlCodeObject) IndexedColumns IndexOptions IsSqlCodeSnippet(Inherited fromSqlCodeObject) ...
( logical_expression ) ] <column_set_definition> ::= column_set_name XML COLUMN_SET FOR ALL_SPARSE_COLUMNS ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ ,... n ] ) [ WITH FILLFACTOR = fillfactor...
column2 data_type[CONSTRAINT constraint_name], ... )[WITH (table_option = value, ...)][INHERITS (parent_table_name)]-- GaussDB 支持继承[PARTITION BY partition_method (column)]-- 分区表定义[DISTRIBUTE BY HASH(column) | RANGE(column)]-- GaussDB 分布式策略[LAYOUT ON (COLUMNS (column1, ...