-- 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 theUNIQUEconstraint defined forcollege_...
What does the SQLUNIQUEconstraint ensure? That a column cannot contain NULL values That all values in a column are different That a column must always contain a value That a column is a foreign key ❮ PreviousNext ❯ Track your progress - it's free!
1、使用sql查询主键的唯一约束当前最大值：select max（id） from table；（id为number类型）select max（to_number(id)） from table;(id为非number类型)2、使用sql查询该表的序列的下一个值 select SEQ.NEXTVAL from dual;（seq是对应表的序列名）3、最后使用PL/SQL客户端编辑序列，将序列的下一...
Applies to:SQL Server 2016 (13.x) and laterAzure SQL DatabaseAzure SQL Managed Instance 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...
SQL UNIQUE Constraint 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. ...
,CONSTRAINT emp_email_uk UNIQUE (email) ... ); Theemp_email_uk constraint ensures that no two employees have the same emailaddress, as shown in Example5-1. Example 5-1 Unique Constraint SQL> SELECT employee_id, last_name,email FROM employees WHERE email = 'PFAY'; ...
,CONSTRAINT emp_email_uk UNIQUE (email) ... ); Theemp_email_uk constraint ensures that no two employees have the same emailaddress, as shown inExample5-1. Example 5-1 Unique Constraint SQL> SELECT employee_id, last_name,email FROM employees WHERE email = 'PFAY'; ...
ALTER TABLE ADD CONSTRAINT UNIQUE(); 实例2,修改数据表 demo_department,指定部门的名称唯一,输入的 SQL 语句和运行结果如下所示。 mysql> ALTER TABLE demo_department -> ADD CONSTRAINT unique_name UNIQUE(name); Query OK, 0 rows affected (0.63 sec) ...
java代码报错：java.sql.BatchUpdateException: ORA-00001: 违反唯一约束条件 (TTT.table)at oracle.jdbc.driver.DatabaseError.throwBatchUpdateException(DatabaseError.java:629)at oracle.jdbc.driver.OraclePreparedStatement.executeBatch(OraclePreparedStatement.java:9447)at oracle.jdbc.driver.OracleStatement...
ISqlUniqueConstraint 类型公开以下成员。 方法 展开表 名称说明 AddAnnotation 将给定批注添加到此元素。 (继承自 IModelAnnotationHolder。) Delete 从模型中删除此实例。 (继承自 IModelElement。) GetAnnotations() 返回附加到此元素的批注的列表。 (继承自 IModelAnnotationHolder。) GetAnnotations(Type) 返回给定...