jointable

问题 I need to create table PORTATION_MODEL_SET. And I need to create two keys from table portation and one key from table phone_model I have code: @Entity @Table(name="PORTATION") @SecondaryTable(name="PORTATION") @Cache(usage=CacheConcurrencyStrategy.NONSTRICT_READ_WRITE) public class JDBCPortation implements Portation { @Id @GeneratedValue(strategy=GenerationType.AUTO) private Integer id; @ManyToOne(targetEntity=JDBCContentMetaData.class, fetch=FetchType.LAZY) @JoinColumn(name="fk_content_id"

问题 im new to SQL and want to know how to replace the below code with SQL joins. I want to list all information based on p_id ='123'. select p.p_name,c.c_name,s.s_name,s.s_contact,b.b_name,b.b_contact from product p, category c, seller s, buyer b where p.p_id="123" and c.p_id="123" and s.p_id="123" and b.p_id="123"; Tables used Product Table p_id p_name Category Table p_id c_id c_name Seller Table p_id s_id s_name s_contact Buyer Table p_id b_id b_name b_contact Thanks 回答1: This is the query

问题 So, I am not sure what the best way to do a join for these tables was. I want to use a JOIN because I believe it is faster than bring all three of the tables in on FROM. So, if i have three tables... Table1 --id --data Table2 --id --data Table1_Table2 --table1_id --table2_id How can I do a join for this data using the join table? 回答1: Mentioning all tables in the FROM clause is also a join, implicit one. It is not recommended to use it as it might lead to a Cartesian product of the tables

问题 I am trying to save an entity that has a many-to-many association to another entity and cascade the persistence to the associated entity and create the association using spring data jpa repository. I can insert the parent entity_a which contains a set of entity_b using entityARepository.save(entityA) . Spring jpa is taking care of all the inserts needed in the transaction. All the entity_b's get inserted, entity_a's get inserted and the join table in the middle has the association inserted as

问题 class Candidate { String username; static HasMany=[applications:Application] } class Vote { String name; Date firstdate; Date enddate ; static HAsMany=[applications:Application] } class Application { Date datedemand; Candidate candidate; Vote vote; static belongsTo = [candidate:Candidate,vote:Vote] } I want to display the list of votes and if I click on a vote, it displays the list of candidates for this vote. I started ​​the following attempt, and I remain blocked : def candidatsGrpByVte(){

问题 so I have an entity named Event which contains many Reports (one to many) which contains many sources (many to many). I'm facing a problem that I just cant figure out, when I'm trying to update my event, it will try to update the report because of the cascade (which is fine) and it will try to update the report's sources on the join table because of the cascade (which is fine), but for some reason it also tries to update the Source entity, which it shouldn't update because there is no change

问题 The other day I asked a question and received some very helpful information which assisted me to get this far. However I am now having trouble with taking data from tables using UNION/GROUP BY. The following code is what I have tried. But I cannot seem to find a way to make it group by Player. It is showing like this. Jono - 3 - 1 Jono - 1 - 1 When I need to show like this Jono - 4 - 1 I am just beginning so if there is a better way to perform this code, please tell me :) SELECT [Player],

问题 I have the following structure: class User < ActiveRecord::Base has_many :device_ownerships has_many :devices, :through => :device_ownerships end class Device < ActiveRecord::Base has_one :device_ownership has_one :user, :through => :device_ownership end class DeviceOwnership < ActiveRecord::Base belongs_to :user belongs_to :device end However DeviceOwnership also has serial_number row I want to pass serial_number value to DeviceOwnership on create. I understand I can do something like def

问题 Im new to cakePHP and the whole table relations concept is very confusing! I have 2 tables, competencies and competenceRatings. competencies stores a list of names with ids. competencies ------------ id name And users can select various competencies from this table and rate them and their ratings are stored into competenceRatings table. competenceRatings ----------------- id competence_id user_id rating I want to be able to get the names of competencies for which a user have NOT made any

问题 Given two entities: Card PurchaseProductGroup , which has a ppg_status column (field named as status on the entity) that can be 'A' (active) or 'D' (deleted) These conceptually have a many-to-many relationship but an explicitly defined join table entity named PurchaseProductGroupCard is used (so an external ID can be assigned for each mapping). So both Card and PurchaseProductGroup have a @OneToMany relationship to PurchaseProductGroupCard , e.g. in Card there is the following: @OneToMany