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- Estou com o o seguinte problema, preciso fazer o mapeamento relacional de um banco, e nesse banco possui a tabela sessao, a qual possui 2 campos de referencia a tabela sala, como posso realizar esse.
- SchemaUpdate javax.persistence.ForeignKey doesn't respect ConstraintMode.NOCONSTRAINT. Alter table oauthclient add constraint FK43dmxuh3574xhqwmvkt8gdwqf.
The ForeignKey annotation is used in schema generation. It is used to define a foreign key constraint or to override or disable the persistence provider’s default foreign key definition. If the join is for a OneToOne or ManyToOne mapping using a foreign key mapping strategy, the foreign key column is in the table of the source entity or embeddable. If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the foreign key.
A key serves as a unique identifier for each entity instance. Most entities in EF have a single key, which maps to the concept of a primary key in relational databases (for entities without keys, see Keyless entities). Entities can have additional keys beyond the primary key (see Alternate Keys for more information).
By convention, a property named
Id
or <type name>Id
will be configured as the primary key of an entity.Note
Owned entity types use different rules to define keys.
You can configure a single property to be the primary key of an entity as follows:
You can also configure multiple properties to be the key of an entity - this is known as a composite key. Composite keys can only be configured using the Fluent API; conventions will never setup a composite key, and you can not use Data Annotations to configure one.
Primary key name
By convention, on relational databases primary keys are created with the name
PK_<type name>
. You can configure the name of the primary key constraint as follows:Key types and values
While EF Core supports using properties of any primitive type as the primary key, including
string
, Guid
, byte[]
and others, not all databases support all types as keys. In some cases the key values can be converted to a supported type automatically, otherwise the conversion should be specified manually.Key properties must always have a non-default value when adding a new entity to the context, but some types will be generated by the database. In that case EF will try to generate a temporary value when the entity is added for tracking purposes. After SaveChanges is called the temporary value will be replaced by the value generated by the database.
Important
If a key property has its value generated by the database and a non-default value is specified when an entity is added, then EF will assume that the entity already exists in the database and will try to update it instead of inserting a new one. To avoid this turn off value generation or see how to specify explicit values for generated properties.
Alternate Keys
An alternate key serves as an alternate unique identifier for each entity instance in addition to the primary key; it can be used as the target of a relationship. When using a relational database this maps to the concept of a unique index/constraint on the alternate key column(s) and one or more foreign key constraints that reference the column(s).
Tip
If you just want to enforce uniqueness on a column, define a unique index rather than an alternate key (see Indexes). In EF, alternate keys are read-only and provide additional semantics over unique indexes because they can be used as the target of a foreign key.
Alternate keys are typically introduced for you when needed and you do not need to manually configure them. By convention, an alternate key is introduced for you when you identify a property which isn't the primary key as the target of a relationship.
You can also configure a single property to be an alternate key:
You can also configure multiple properties to be an alternate key (known as a composite alternate key):
Foreign Key In Mysql
Finally, by convention, the index and constraint that are introduced for an alternate key will be named
AK_<type name>_<property name>
(for composite alternate keys <property name>
becomes an underscore separated list of property names). You can configure the name of the alternate key's index and unique constraint:Javax Persistence Query
Element Detail
name
(Optional) The name of the foreign key column. The table in which it is found depends upon the context.- If the join is for a OneToOne or ManyToOne mapping using a foreign key mapping strategy, the foreign key column is in the table of the source entity or embeddable.
- If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the foreign key is in the table of the target entity.
- If the join is for a ManyToMany mapping or for a OneToOne or bidirectional ManyToOne/OneToMany mapping using a join table, the foreign key is in a join table.
- If the join is for an element collection, the foreign key is in a collection table.
Default (only applies if a single join column is used): The concatenation of the following: the name of the referencing relationship property or field of the referencing entity or embeddable class; '_'; the name of the referenced primary key column. If there is no such referencing relationship property or field in the entity, or if the join is for an element collection, the join column name is formed as the concatenation of the following: the name of the entity; '_'; the name of the referenced primary key column.- Default:
- '
referencedColumnName
(Optional) The name of the column referenced by this foreign key column.- When used with entity relationship mappings other than the cases described here, the referenced column is in the table of the target entity.
- When used with a unidirectional OneToMany foreign key mapping, the referenced column is in the table of the source entity.
- When used inside a
JoinTable
annotation, the referenced key column is in the entity table of the owning entity, or inverse entity if the join is part of the inverse join definition. - When used in a
CollectionTable
mapping, the referenced column is in the table of the entity containing the collection.
Default (only applies if single join column is being used): The same name as the primary key column of the referenced table.- Default:
- '
unique
(Optional) Whether the property is a unique key. This is a shortcut for theUniqueConstraint
annotation at the table level and is useful for when the unique key constraint is only a single field. It is not necessary to explicitly specify this for a join column that corresponds to a primary key that is part of a foreign key.- Default:
- false
nullable
(Optional) Whether the foreign key column is nullable.- Default:
- true
insertable
(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.- Default:
- true
updatable
(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.- Default:
- true
columnDefinition
(Optional) The SQL fragment that is used when generating the DDL for the column.Defaults to the generated SQL for the column.- Default:
- '
table
(Optional) The name of the table that contains the column. If a table is not specified, the column is assumed to be in the primary table of the applicable entity.Default:- If the join is for a OneToOne or ManyToOne mapping using a foreign key mapping strategy, the name of the table of the source entity or embeddable.
- If the join is for a unidirectional OneToMany mapping using a foreign key mapping strategy, the name of the table of the target entity.
- If the join is for a ManyToMany mapping or for a OneToOne or bidirectional ManyToOne/OneToMany mapping using a join table, the name of the join table.
- If the join is for an element collection, the name of the collection table.
- Default:
- '
foreignKey
(Optional) Used to specify or control the generation of a foreign key constraint when table generation is in effect. If this element is not specified, the persistence provider's default foreign key strategy will apply.- Since:
- Java Persistence 2.1
- Default:
- @javax.persistence.ForeignKey(javax.persistence.ConstraintMode.PROVIDER_DEFAULT)