relationship

问题 So, I'm receiving the following error from Laravel framework; but I couldn't find why this framework is producing this error: SQLSTATE[42000]: Syntax error or access violation: 1066 Not unique table/alias: 'participants' (SQL: select `participants`.*, `participants`.`message_id` as `pivot_message_id`, `participants`.`user_id` as `pivot_user_id`, `participants`.`created_at` as `pivot_created_at`, `participants`.`updated_at` as `pivot_updated_at` from `participants` inner join `participants` on

问题 Would someone kindly assist me with the following? I have two DataGridView objects that each display a DataTable, where the two datatables are related with the following code: DataSet dSet = new DataSet(); DataTable ParentList = ListToDataTable(_listOfAllAlbumObjects); DataTable ChildList = ListToDataTable(_listOfAllTrackObjects); dSet.Tables.AddRange(new DataTable[]{ParentList, ChildList}); DataColumn parentRelationColumn = ParentList.Columns["AlbumId"]; DataColumn childRelationColumn =

问题 Would someone kindly assist me with the following? I have two DataGridView objects that each display a DataTable, where the two datatables are related with the following code: DataSet dSet = new DataSet(); DataTable ParentList = ListToDataTable(_listOfAllAlbumObjects); DataTable ChildList = ListToDataTable(_listOfAllTrackObjects); dSet.Tables.AddRange(new DataTable[]{ParentList, ChildList}); DataColumn parentRelationColumn = ParentList.Columns["AlbumId"]; DataColumn childRelationColumn =

问题 How to add conditions to the relation? For example, we have object Pet @Entity public class Pet { @ PrimaryKey int id; int userId; String name; String type; // other fields } and object User public class User { int id; // other fields } For getting user with pets we make object public class UserAllPets { @Embedded public User user; @Relation(parentColumn = "id", entityColumn = "userId", entity = Pet.class) public List<PetNameAndId> pets; } How is possible to get user with pets by type? Only

问题 I am working on an application that will be used as an extensible framework for other applications. One of the fundamental classes is called Node, and Nodes have Content. The SQL tables look like this: TABLE Node ( NodeId int, .... etc ) TABLE NodeContentRelationship ( NodeId int, ContentType string, ContentId int) It will be up to the developers extending the application to create their own content types. Clearly this is bad from a relationship-database point of view as it is not possible to

问题 I am stuck in a problem where i have to find cardinality of a relationship between tables using mysql. Following this post MySQL: How to determine foreign key relationships programmatically? I have found all tables related to my table and the columns which are foreign key. Now i also want to find the cardinality of relationship i.e. one-to-one, one-to-many or many-to-many. Any ideas or snippets would be highly appreciated 回答1: Let us assume that table A has a foreign key f which refers to the

问题 I am stuck in a problem where i have to find cardinality of a relationship between tables using mysql. Following this post MySQL: How to determine foreign key relationships programmatically? I have found all tables related to my table and the columns which are foreign key. Now i also want to find the cardinality of relationship i.e. one-to-one, one-to-many or many-to-many. Any ideas or snippets would be highly appreciated 回答1: Let us assume that table A has a foreign key f which refers to the

问题 I have two tables, shipments and customers. In the real world, a customer can be related to a shipment in three ways: as the biller, the destination and/or the origin. So my question here is, do I have a pivot table with three columns, one for the shipment_id, one for the customer_id, and one for the relationship_type id? Or do I have separate tables? I'm not sure how best to approach this as it's the first of it's kind that I've run up against. 回答1: I faced this couple weeks ago and I came

问题 I have two tables, shipments and customers. In the real world, a customer can be related to a shipment in three ways: as the biller, the destination and/or the origin. So my question here is, do I have a pivot table with three columns, one for the shipment_id, one for the customer_id, and one for the relationship_type id? Or do I have separate tables? I'm not sure how best to approach this as it's the first of it's kind that I've run up against. 回答1: I faced this couple weeks ago and I came

问题 I do have swatches table, a colors table and a swatch_color pivot table. Relations are set as: public function colors() { return $this->belongsToMany('Color'); } public function swatches() { return $this->belongsToMany('Swatch'); } I have no problem to retrieve the swatches with the color relations $swatches = Swatch::with('colors')->get(); return dd($swatches); Colors is always an array of 5 color objects with hue, R, G, and B attributes. Now I would like to sort the swatches by the R value