方法一、使用add constraint 方法添加主键约束 alter table 表名 add constraint 主键名 primary key (列名1,列名2,...) 方法二、使用索引创建主键 (和方法一没有区别,可以将方法一理解为省略了using index) alter table 表名 add constraint 主键名 primary key (列名1,列名2,...) using index [index_name...
根据报错,貌似是primary key创建失败导致的。 代码语言:javascript 复制 SQL>ALTERTABLET12ADDCONSTRAINTT1_PK3PRIMARYKEY(BEN)USINGINDEX(CREATEUNIQUEINDEXT1_PKONT1(BEN)PCTFREE10INITRANS2TABLESPACEPOOL_IXLOGGINGSTORAGE(INITIAL16384NEXT16384MINEXTENTS1MAXEXTENTS400PCTINCREASE0FREELISTS1))4567891011;ALTERTABLET1*ERRORa...
数据库键(key)、主键(primaryKey)、索引(index)、唯一索引(uniqueIndex)区别,程序员大本营,技术文章内容聚合第一站。
由于本文是基于mysql的InnoDB存储引擎,索引我们主要看第一个表格,其他的表格可以自行的观看,都不难,从表格我们可以看出来,InnoDB存储引擎索引只支持BTREE类型的索引,索引的类别有Primary Key,Unique,Key,FULLTEXT和SPATIAL。当然也有其他的分法,按照索引列的数量分为单列索引和组合索引。 Primary Key(聚集索引):InnoDB...
PRIMARY KEY (`id`) USING BTREE unique key(唯一性约束) 1.一张表可以有多个唯一性约束,通常限制非主键列 2.没有重复值但允许为空(NULL) 3.不可作为外键 4.只要唯一就可以更新 使用语法: CREATE [ UNIQUE | FULLTEXT ] INDEX index_name ON table_name (index_col_name, ...); ...
ALTER TABLE TEST.RF_TEST ADD CONSTRAINT PK_RF_TEST PRIMARY KEY(ID) USING INDEX TABLESPACE TEST_DATA; 1. 1. ALTER TABLE TEST.RF_TEST ADD CONSTRAINT FK_RF_TEST FOREIGN KEY(OBJECT_ID ) REFERENCES TEST.TEST(OBJECT_ID); 1. 如下所示,由于脚本上面的原因(没有指定主键约束对应的索引,而且又有其...
Access automatically creates an index for the primary key, which helps speed up queries and other operations. Access also ensures that every record has a value in the primary key field, and that it is always unique. When you create a new table in Datasheet view, Acces...
Re: primary key vs covered index 723 marcin kot December 01, 2016 04:16AM Re: primary key vs covered index 696 Øystein Grøvlen December 01, 2016 04:25AM Sorry, you can't reply to this topic. It has been closed. Content reproduced on this site is the property of the respective ...
By using PRIMARY KEY, we can identify single row uniquely. Advantages - By using PRIMARY KEY, we can DELETE or UPDATE specific records from table by identifying uniquely instead of multiple records on table. We can fetch data quickly by using primary key with the help of clustered index. PRI...
此範例示範Index的PrimaryKey和Unique屬性。 此程式碼會建立具有兩個資料行的新資料表。PrimaryKey和Unique屬性用來使一個資料行成為不允許重複值的主索引鍵。 複製 // BeginPrimaryKeyCpp.cpp // compile with: /EHsc #import "msado15.dll" rename("EOF", "EndOfFile") #import "msadox.dll" no_nam...