composite-primary-key | 易学教程

How can I define a composite primary key in SQL?

阅读更多关于 How can I define a composite primary key in SQL?

How can I define a composite primary key consisting of two fields in SQL? I am using PHP to create tables and everything. I want to make a table name voting with fields QuestionID , MemeberID , and vote . And the Composite primary key consists of the fields QuestionID and MemberID . How should I do this? Just for clarification: a table can have at most one primary key. A primary key consists of one or more columns (from that table). If a primary key consists of two or more columns it is called a composite primary key . It is defined as follows: CREATE TABLE voting ( QuestionID NUMERIC,

What Kind of Relationship is Between These Tables?

阅读更多关于 What Kind of Relationship is Between These Tables?

问题 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.

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

阅读更多关于 Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?

问题 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

How I can put composite keys in models in Laravel 5?

阅读更多关于 How I can put composite keys in models in Laravel 5?

I have in my DataBase a table with two primary keys (id and language_id) and I need put it in my models. The default primaryKey in Models (Model.php in Laravel 5) is id, and I want that the primaryKeys will be id and id_language. I tried put it with arrays or a String with ',' but it doesn't work. It says me that the array could not be converted in String. Please Help. Thanks! You can't. Eloquent doesn't support composite primary keys. Here's a Github issue regarding this. I wrote this simple PHP trait to adapt Eloquent to handle composite keys: <?php namespace App\Model\Traits; // *** Adjust

How to create and handle composite primary key in JPA

阅读更多关于 How to create and handle composite primary key in JPA

I want to have versions from the same data entry. In other words, I want to duplicate the entry with another version number. id - Version will be the primary key. How should the entity look like? How can I duplicate it with another version? id Version ColumnA 1 0 Some data 1 1 Some Other data 2 0 Data 2. Entry 2 1 Data Rohit Jain You can make an Embedded class , which contains your two keys, and then have a reference to that class as EmbeddedId in your Entity . You would need the @EmbeddedId and @Embeddable annotations. @Entity public class YourEntity { @EmbeddedId private MyKey myKey; @Column

How to update primary key

阅读更多关于 How to update primary key

问题 Here is my problem: I have 2 tables: WORKER, with columns |ID|OTHER_STAF| , where ID is primary key FIRM, with columns |FPK|ID|SOMETHING_ELSE| , where combination FPK and ID make primary key, and also ID is a foreign key referenced to WORKER.ID (not null, and must have same value as in WORKER). I want to make stored procedure UPDATE_ID_WORKER, where I would like to change the value of specific ID in WORKER, and also in all instances of specific value of ID in FIRM. stored procedure: ........

Composite primary key or not?

阅读更多关于 Composite primary key or not?

问题 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

ALTER TABLE to add a composite primary key

阅读更多关于 ALTER TABLE to add a composite primary key

问题 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? 回答1: 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

How to create and handle composite primary key in JPA

阅读更多关于 How to create and handle composite primary key in JPA

问题 I want to have versions from the same data entry. In other words, I want to duplicate the entry with another version number. id - Version will be the primary key. How should the entity look like? How can I duplicate it with another version? id Version ColumnA 1 0 Some data 1 1 Some Other data 2 0 Data 2. Entry 2 1 Data 回答1: You can make an Embedded class , which contains your two keys, and then have a reference to that class as EmbeddedId in your Entity . You would need the @EmbeddedId and

Sqlite primary key on multiple columns

阅读更多关于 Sqlite primary key on multiple columns

问题 What is the syntax for specifying a primary key on more than 1 column in SQLITE ? 回答1: According to the documentation, it's CREATE TABLE something ( column1, column2, column3, PRIMARY KEY (column1, column2) ); 回答2: CREATE TABLE something ( column1 INTEGER NOT NULL, column2 INTEGER NOT NULL, value, PRIMARY KEY ( column1, column2) ); 回答3: Yes. But remember that such primary key allow NULL values in both columns multiple times. Create a table as such: sqlite> CREATE TABLE something ( column1,