unique-constraint

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Are unique constraints on the DB necessary?

I\'ve been wondering lately. Lets say we\'re doing a webapp with JSF+Spring+JPA/Hibernate (or well any other technologies) and lets say we have a \"User\" entity. We want the User to have a unique log[详细]

2023-01-13 23:26 分类：问答
Unique constraint using data in multiple tables (SQL / SQLAlchemy)

A top class called Parametric is used to create objects which can have parameters associated with them:[详细]

2023-01-13 00:09 分类：问答
SQL: How to find duplicates based on two fields?

I have rows in an Oracle database table which should be unique for a combination of two fields but the unique constrain is not set up on the table so I need to find all rows which violate the constrai[详细]

2023-01-12 11:37 分类：问答
Hibernate and NonUniqueObjectException

i have an entity that contains two other entities with @ManyT开发者_开发知识库oOne relationship.[详细]

2023-01-12 10:25 分类：问答
Lost transaction with JPA unique constraint?

I have a field with an unique constraint: @Column(unique=true) private String uriTitle; When I try to save two entities with the same value, I get an exception - but another exception than I execte[详细]

2023-01-12 08:55 分类：问答
Hibernate throws unique constraint violation exception while updating field part of unique key

Below is the use case: I have a unique index defined on 3 columns say A,B,C. Assume the values in them are A1,B1,C开发者_StackOverflow1.[详细]

2023-01-12 02:07 分类：问答
HowTo: display custom error message when unique index fails on object save

I have add开发者_如何学编程ed an index on a table just to ensure that a set of fields together form a composite unique key (Is this approach correct? or is there a better option with Doctrine?)[详细]

2023-01-10 12:00 分类：问答
Unique Constraint vs Unique Index

I’m interested in learning which technique developers prefer to use to enforce uniqueness in SQL Server:UNIQUE CONSTRA开发者_运维百科INT or UNIQUE INDEX.Given that there is little difference in the p[详细]

2023-01-08 17:12 分类：问答
Catching constraint violations in JPA 2.0

Consider the following entity class, used with, for example, EclipseLink 2.0.2 - where the link attribute is not the开发者_JS百科 primary key, but unique nontheless.[详细]

2022-12-31 14:08 分类：问答
Why getting active record error when trying to work on arrays?

I have the following association in my User model: has_and_belongs_to_many :friends, :class_name =>开发者_运维百科; \'User\', :foreign_key => \'friend_id\'[详细]

2022-12-30 18:00 分类：问答