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    展开全文
  • laravel 插入数据的时候,任我怎么插入,也还是这个错误, 不懂为什么我的主键的id ,之前的数据有一条值为‘0’。 这条错误是 违反完整性约束; 把id为0 的改了,就可以了...

    laravel 插入数据的时候,任我怎么插入,也还是这个错误, 不懂为什么我的主键的id ,之前的数据有一条值为‘0’。
    这条错误是

    违反完整性约束;

    把id为0 的改了,就可以了

    展开全文
  • 昨天为了删除数据库表中的字段,使用了alter tabledrop columncolumnName服务器返回的错误为:Server: Msg 5074, Level 16, State 1, Line 1The object 'DF__Test__columnName__351DDF8C' is dependent on column '...

    昨天为了删除数据库表中的字段,使用了

    alter table

    drop column

    columnName

    服务器返回的错误为:

    Server: Msg 5074, Level 16, State 1, Line 1The object 'DF__Test__columnName__351DDF8C' is dependent on column 'columnName'.

    Server: Msg 4922, Level 16, State 1, Line 1

    ALTER TABLE DROP COLUMN columnName failed because one or more objects access this column.

    我进入企业管理器中却可以删除,

    经过检查发现该字段设置有默认值,其实设置了默认值就相当于设置了约束,在Sql Server 2000中约束有以下几种:

    1 primary key 主键约束

    2 foreign key 外键约束

    3 unique 唯一约束

    4 check 检查约束

    5 default 默认值约束

    其中 primary key 主键约束 和 unique 唯一约束 相似但是还是有细微区别:

    unique在下面两个情况下可以使用:

    1 unique约束可以多个列组合,一个表只可以有一个primary key 约束,而可以有多个unique约束。

    2 primary key 约束不能有null,而unique约束可以有null值。

    foreign key 和 check约束有相似也有区别

    foreign key 约束通过从另外一个表获得有效数值列表,而check约束是从设置在表中的逻辑表达式来判断的。

    那现在的问题是:我可以在企业管理器中删除有约束的列而在程序中用:

    alter table

    drop column

    columnName却会出错,那么必须在删除列的时候先删除该列相关的约束了,还好现在是internet时代,上网搜索了一下发现有如下解决方法:

    if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[p_deletefield]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)

    drop procedure [dbo].[p_deletefield]

    GO

    /*--删除某字段的所有关系及该字段

    删除某字段时,常常因为在该字段上定义了约束/外键/默认值

    导致字段删除失败,此存储过就是删除表中指定字段的这些关系

    修正2004.05发布的删除处理中的错误,同时改原来的处理语句为通用存储过程

    --邹建 2004.07--*/

    /*--调用示例

    exec p_deletefield '表名','字段名'

    --*/

    create proc p_deletefield

    @tbname sysname, --要处理的表名

    @fdname sysname, --要处理的字段名

    @delfield bit=1  --0只删除关系,1同时删除字段

    as

    declare hCForEach cursor global for

    --默认值约束

    select sql='alter table ['+b.name+'] drop constraint ['+d.name+']'

    from syscolumns a

    join sysobjects b on a.id=b.id and a.name=@fdname and b.name=@tbname

    join syscomments c on a.cdefault=c.id

    join sysobjects d on c.id=d.id

    union --外键引用

    select s='alter table ['+c.name+'] drop constraint ['+b.name+']'

    from sysforeignkeys a

    join sysobjects b on b.id=a.constid

    join sysobjects c on c.id=a.fkeyid

    join syscolumns d on d.id=c.id and a.fkey=d.colid and d.name=@fdname

    join sysobjects e on e.id=a.rkeyid and e.name=@tbname

    join syscolumns f on f.id=e.id and a.rkey=f.colid

    union --主键/唯一键/索引

    select case when e.xtype in('PK','UQ') then 'alter table ['+c.name+'] drop constraint ['+e.name+']'

    else 'drop index ['+c.name+'].['+a.name+']' end

    from sysindexes a

    join sysindexkeys b on a.id=b.id and a.indid=b.indid

    join sysobjects c on b.id=c.id and c.xtype='U' and c.name=@tbname

    join syscolumns d on b.id=d.id and b.colid=d.colid and d.name=@fdname

    left join sysobjects e on e.id=object_id(a.name)

    where a.indid not in(0,255)

    exec sp_msforeach_worker '?'

    if @delfield=1

    exec('alter table ['+@tbname+'] drop column ['+@fdname+']')

    go

    展开全文
  • 使用数据库UNIQUE constraint failed

    万次阅读 2017-07-31 10:24:19
    Encounter local execpiton: android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed: greendao-db._id (code 1555)违反唯一性约束 你对表做create和update的时候对该字段的插入值重复了
    Encounter local execpiton: android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed: greendao-db._id (code 1555)

    违反唯一性约束 你对表做create和update的时候对该字段的插入值重复了

    展开全文
  • 数据库约束(constraint)约束的目的:对表中的数据进行条件限制,保证表中的记录完整和有效性目录:15.1非空约束(not null)15.2唯一性约束(unique)15.3组合使用 not null 和 unique15.4主键约束PK(primary key)15.5...
  • Caused by: java.sql.SQLException: Cannot add foreign key constraint查看DATABASECHANGELOG 日志 使用h2数据库时,liquibase是能够正确创建表和外键以及索引,但是换到mysql的时候,无法成功创建外键。手动执行...
  • 13_约束constraint
  • 1.什么是约束(Constraint)       在创建表的时候,可以给表的字段添加相应的约束,添加约束的目的是为了保证表中数据的合法性、有效性、完整性。 2.常见的约束 非空约束(not null...
  • Constraint name uniqueness 这个问题是因为powerdesigner从CDM转PDM时,生成的Constraint name 重复导致的。 原因:Constraint name必须是一定长度之内的,而powerdesigner从CDM转PDM时,Constraint name的...
  • 近期在做一个功能测试时,需要往DB2数据库中插入一条数据,插入时,一直报“......SQLERRMC=WCSADMIN.MANIFEST.F_428,.....”错误,通过DbVisualizer Personal工具查看该表,显示有一个 F_428外键约束,但是无奈,...
  • 我们在创建数据库的时候会创建一些Constraint约束,包括主键、外键等。那么约束它有属性吗?答案是肯定的,本文我们就介绍一下Oracle数据库Constraint约束的四对属性:Deferrable/not deferrab...
  • 最近一张表上有两列字段,要求这两列要么都有值,要么都为空,简单的table定义没办法实现这种要求,需要利用Oracle的constraint(约束)机制。约束主要是用来保证数据的完整性。  可以从TOAD的设置上,很容易看到...
  • 我们在创建数据库的时辰会创建一些Constraint束缚,包含主键、外键等。那么束缚它有属性吗?答案是必然的,本文我们就介绍一下Oracle数据库Constraint束缚的四对属性:Deferrable/not deferrable, Deferred/...
  • !!!注意: 读此篇文章前,如果有key概念不懂,请见我的博客: ...数据库中7个Constraint(约束)的概念区分 Key Constraint: key值不可重复 candidate key can not be duplicated. Entity Constraint:...

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