jointable

I Have three tables in my database users , posts and comments. Their Structure is as follow : **users** : user_id , user_name **posts**: post_id , post_content, user_id **comments** : comment_id , comment_content , post_id, user_id now i want to fetch data from these three tables using join in a following way : comment_id, comment_content, user_id, user_name, post_id can anyone plz tell me that how this can be done ? I Shall be very thankful. It's a simple JOIN . Try this: select c.comment_id, c.comment_content, u.user_id, u.user_name, c.post_id from comments c join users u on u.user_id = c

I'm using ROOM for my project. But I'm having trouble for joining between tables, because the tables have a same name fields. for example, my project has tree tables, "word" & "favorite" & "bookmark", which has a same name fields. 1- word @Entity(tableName = "word") public class Word { @NonNull @PrimaryKey(autoGenerate = true) private int id; @NonNull private String title; private String mean; private String pronunciation; // Getter and Setter } 2- favorite @Entity(tableName = "favorite", foreignKeys = @ForeignKey( entity = Word.class, parentColumns = "id", childColumns = "word_id", onDelete =

This is my annotation I use to generate my Join Table. @OneToMany(cascade = CascadeType.ALL) @JoinTable(name = "service_operations", joinColumns = { @JoinColumn(name = "serviceId") }, inverseJoinColumns = { @JoinColumn(name = "operationId") }) public Set<Operation> getOperations() { return operations; } Considering this is a OneToMany association, my natural assumption is that this table would generate a [ Primary Key | Foreign Key ] table, however everytime I drop and re create the database it is not the case: mysql> describe workflow_services; +-------------+------------+------+-----+-------

I've got two tables and a join table: 'staff', 'classification' and 'staff_classification'. In the join table I've got an extra boolean field: 'showclassification'. My annotation is as follows: /** * @ManyToMany(targetEntity="Staff", inversedBy="classifications") * @JoinTable(name="staff_classifications", * joinColumns={@JoinColumn(name="staffid", referencedColumnName="id")}, * inverseJoinColumns={@JoinColumn(name="classificationid", referencedColumnName="id", unique=true)}); */ How do I add the extra field 'showclassifications' to the join table? How do I reference the field via DQL? E.g.

I have a question for designing the ManyToMany in EJB, how can a jointable has a property? Here is an example, the students and courses are ManyToMany, every student have many courses, and many students choose one course. @Entity public class Student implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) Long id; String name; private Collection<Course> courses; @ManyToMany(mappedBy = "students",cascade=CascadeType.ALL) public Collection<Course> getCourses() { return this.courses; } public void setCourses(Collection<Course> courses) { this.courses = courses; } } @Entity

I've discovered a nice way to generate join tables for my HABTM relationships in my Rails app. rails g migration CreateJoinTable table1 table2 This generates an ActiveRecord::Migration that employs the method create_join_table I'm wondering what this wonderful mysterious method does. I guess it makes a table (probably without an id field) that has a column for table1 foreign key and a column for table2 foreign key, but does the table have any other features?. My habit for join tables has always been to add a unique index across both those columns so that a relationship between a record in