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...
'` USING ', INDEX_TYPE )END,IF(UPPER(INDEX_NAME) = 'PRIMARY', CONCAT('PRIMARY KEY USING ', INDEX_TYPE ),CONCAT('UNIQUE INDEX `', INDEX_NAME, '` USING ', INDEX_TYPE))),'(', GROUP_CONCAT(DISTINCT CONCAT('`', COLUMN_NAME, '`') ORDER BY SEQ_IN_INDEX ASC SEPARATOR ', '),...
The customer ID field is the primary key. 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 cr...
It tries to drop the index of theIceCreamIdcolumn, even though it is theAccidentalIdcolumn that is being relieved from being the primary key, before it is later dropped completely. This does not happen if the index has been explicitly defined in the model. ...
I want to add new field as primary key to old model (there was no primary key in my model but the contents are unique), but in migration i got this error: java.lang.IllegalArgumentException: Illegal Argument: Field "projectUniqueKey" can...
Using this method, you cannot create a composite primary key:[cc lang=”sql”] CREATE TABLE [dbo].[Person]( PersonID [int] IDENTITY(1,1) CONSTRAINT PK_Person PRIMARY KEY NONCLUSTERED NOT NULL, FirstName VARCHAR(50) NULL ) [/cc]
For efficiency, an index should be organized from the most granular column (highest number of unique values) to the least granular column.The three types of indices that are used in finance and operations apps are:Primary index - Provides a unique key to each record in a table. The ...
Setting a primary key Unless you have a specific reason not to, you should specify a primary key for a table. Access automatically creates an index for the primary key, which can help improve database performance. Access also makes sure that every record has a value in the primary key fiel...
false clears all columns except the declared primary key and ROWGUID columns. Columns are added by using sp_mergearticlecolumn.[ @auto_identity_range = ] N'auto_identity_range'Enables and disables automatic identity range handling for this table article on a publication at the time it's created...
Bug #644 crash in add_key_field when using prepared statements Submitted: 12 Jun 2003 14:56Modified: 11 Mar 2004 8:59 Reporter: Dennis Haney Email Updates: Status: Can't repeat Impact on me: None Category: MySQL ServerSeverity: S1 (Critical) Version: 4.1OS: Linux (linux 2.4) ...