2 VALUES(cons_sequence.nextval,'Jack','Robinson@hotmail.com',2400,20); INSERT INTO tb_constraint_2 * ERROR at line 1: ORA-00001: unique constraint (ROBINSON.UN_TB_CONS2_EMAIL) violated d.CHECK约束提示 --提示check约束sal字段冲突 SQL> INSERT INTO tb_constraint_2 2 VALUES(cons_sequence.ne...
报错:Feature not supported: INSERT on conflict contains un-unique column 问题原因:INSERT ON CONFLICT中的conflict条件使用了非主键字段。 解决方法:INSERT ON CONFLICT中的conflict条件只能使用主键。 报错:Feature not supported: UPDATE with shard keys ...
create tablecourse(cidint(3),cnamevarchar(20),tidint(3));create tableteacher(tidint(3),tnamevarchar(20),tcidint(3));create tableteacherCard(tcidint(3),tcdescvarchar(200));# 插入数据 insert into coursevalues(1,'java',1);insert into coursevalues(2,'html',1);insert into coursevalues(3...
CREATE UNIQUE INDEX for Unique Values 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...
EXECSQLcreatetablet1(id numbernotnullprimarykey,name varchar2(50)notnull,unique(name))partitionbyhash(id)partitions8;//arr_id 一维数组intarr_id[2];EXECSQLselectidinto:arr_idfromt1whereid>1andid<4orderbyid;printf("支持 arr_name 二维数组存字符串,行为个数,列为长度 \n");//arr_mix 二维数...
UNIQUE索引既可以采用聚集索引结构,也可以采用非聚集索引的结构,如果不指明采用的索引结构,则SQL Server系统默认为采用非聚集索引结构。 1.42 删除索引语法: DROP INDEX table_name.index_name[,table_name.index_name] 说明:table_name: 索引所在的表名称。
validation occurs in the same manner, and the query optimizer does not differentiate between a unique index created by a constraint or manually created. However, you should create a UNIQUE constraint on the column when data integrity is the objective. This makes the objective of the index clear...
UNIQUE - 唯一 (表示确定的,只有一个该字段) PRIMARY KEY - 主键 (不能为空, 唯一, 在一个表中最好设置主键) FOREIGN - 外键 (数据库中有连表查询功能, 另外一张表的主键就是当前表的外键) CHECK - 条件检查, 确保一列中的所有值满足一定条件 (CHECK在满足条件时会用到) ...
UNIQUE:唯一,用于保证该字段的值具有唯一性,可以为空。 FOREIGN KEY:外键,用于限制两个表的关系,用于保证该字段的值必须来自于主表的关联列的值,在从表添加外键约束,用于引用主表中某些的值。 约束可应用在列级或表级。列表所有约束均支持,但外键约束没有效果;表级约束可以支持主键、唯一、外键约束。 删除约束 ...
SQL UNIQUE Constraint on ALTER TABLE To create a UNIQUE constraint on the "ID" column when the table is already created, use the following SQL: MySQL / SQL Server / Oracle / MS Access: ALTERTABLEPersons ADDUNIQUE(ID); To name a UNIQUE constraint, and to define a UNIQUE constraint on mu...