composite-primary-key | 易学教程

What Kind of Relationship is Between These Tables?

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I have two tables that have foreign keys to each other's primary key. This DB is in French. I will translate the two tables that I want to you to understand. Atelier Cuisine ==> Kitchen Cuisinier == > Cooking chef So in this picture we see that in the Kitchen table we have a PK referenced by the FK from the Cooking chef table; in the Cooking chef table we have a PK referenced by the FK from the Kitchen table. So I am confused. I don't understand this kind of relationship between these tables. And I hope to check my query that I did to create these two tables if its correct CREATE TABLE

SQL Server “pseudo/synthetic” composite Id(key)

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Sorry but I don't know how to call in the Title what I need. I want to create an unique key where each two digits of the number identify other table PK. Lets say I have below Pks in this 3 tables: Id Company Id Area Id Role 1 Abc 1 HR 1 Assistant 2 Xyz 2 Financial 2 Manager 3 Qwe 3 Sales 3 VP Now I need to insert values in other table, I know that I may do in 3 columns and create a Composite Key to reach integrity and uniqueness as below: Id_Company Id_Area Id_Role ...Other_Columns..... 1 2 1 1 1 2 2 2 2 3 3 3 But I was thinking in create a single column where each X digites identify each FK.

SQL Primary Key - is it necessary?

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问题 I have a list of items. Most of these items will not be in stock. The item table has id, name, description. The quantities of items are stored in another table named inventory. The inventory table has item_id and quantity of items that are in stock. Do I need a primary key for the inventory table? If so, should I use a serial or composite key? When is it ok for a table to not have a primary key? Edit: Thank you all for being very informative. I will now always have primary keys except in very

Cassandra: choosing a Partition Key

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问题 I'm undecided whether it's better, performance-wise, to use a very commonly shared column value (like Country ) as partition key for a compound primary key or a rather unique column value (like Last_Name ). Looking at Cassandra 1.2's documentation about indexes I get this: " When to use an index : Cassandra's built-in indexes are best on a table having many rows that contain the indexed value. The more unique values that exist in a particular column, the more overhead you will have, on

JPA/Hibernate: What's better for composite primary keys, @IdClass or @EmbeddedId implementations and why?

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问题 what's better for JPA/Hibernate composite primary keys, @IdClass or @EmbeddedId implementations and why? This is an intentionally naive question. I decided to use @EmbeddedId (for whatever reason) and I feel like I made the wrong choice. Dereferencing the embeddedId that contains the column properties is redundant and quite error-prone when coding. Are there any more reasons for and/or against the other? Is the a recommendation by the JPA (spec)? 回答1: First, if possible, avoid composite ids

Foreign key relationship with composite primary keys in SQL Server 2005

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问题 I have two tables Table1( FileID, BundledFileID, Domain) and Table2( FileID, FileType, FileName) In Table2 FileID and FileType are the composite primary key. I want to create a foreign key relationship from Table1.FileID to Table2 . Is it possible to do this? 回答1: Since Table2 has a composite primary key (FileID, FileType) , then any reference to it must also include both columns . ALTER TABLE dbo.Table1 ADD CONSTRAINT FK_Table1_Table2 FOREIGN KEY(FileID, FileType) REFERENCES Table2(FileID,

Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?

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When implementing composite primary keys in Hibernate or other ORMs there are up to three places where to put the insertable = false, updatable = false in composite primary key constellations that use identifying relationships (FKs that are part of the PK): Into the composite PK class' @Column annotation (@Embeddable classes only) or Into the entity class' association @JoinColumn/s annotation or Into the entity class' redundant PK property's @Column annotation (@IdClass classes only) The third is the only way to do with @IdClass and JPA 1.0 AFAIK. See http://en.wikibooks.org/wiki/Java

Laravel Model with Two Primary Keys update [duplicate]

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问题 This question already has an answer here: How I can put composite keys in models in Laravel 5? 7 answers I'm trying to update Model which has two primary keys. Model namespace App; use Illuminate\Database\Eloquent\Model; class Inventory extends Model { /** * The table associated with the model. */ protected $table = 'inventories'; /** * Indicates model primary keys. */ protected $primaryKey = ['user_id', 'stock_id']; ... Migration Schema::create('inventories', function (Blueprint $table) {

Composite primary key or not?

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Here's what's confusing me. I often have composite primary keys in database tables. The bad side of that approach is that I have pretty extra work when I delete or edit entries. However, I feel that this approach is in the spirit of database design. On the other side, there are friends of mine, who never use composite keys, but rather introduce another 'id' column in a table, and all other keys are just FKs. They have much less work while coding delete and edit procedures. However, I do not know how they preserve uniqueness of data entries. For example: Way 1 create table ProxUsingDept (

ALTER TABLE to add a composite primary key

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I have a table called provider . I have three columns called person , place , thing . There can be duplicate persons, duplicate places, and duplicate things, but there can never be a dupicate person-place-thing combination. How would I ALTER TABLE to add a composite primary key for this table in MySQL with the these three columns? ALTER TABLE provider ADD PRIMARY KEY(person,place,thing); If a primary key already exists then you want to do this ALTER TABLE provider DROP PRIMARY KEY, ADD PRIMARY KEY(person, place, thing); @Adrian Cornish's answer is correct. However, there is another caveat to