foreign-keys

问题 I have set up ssh key pairs between my desktop and two servers, and from the servers to my desktop, but after reinstalling the OS on my desktop, I can't re-establish the keypair going into my desktop by this: mkdir ~/.ssh chmod 700 ~/.ssh ssh-keygen -t ssh-copy-id username@server I get the following error: (names in italics changed to protect the innocent My desktop is Ubuntu, and I can't find the answer here) @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST

问题 I have set up ssh key pairs between my desktop and two servers, and from the servers to my desktop, but after reinstalling the OS on my desktop, I can't re-establish the keypair going into my desktop by this: mkdir ~/.ssh chmod 700 ~/.ssh ssh-keygen -t ssh-copy-id username@server I get the following error: (names in italics changed to protect the innocent My desktop is Ubuntu, and I can't find the answer here) @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST

问题 I have two tables: CREATE TABLE first_table( my_id TEXT(6) NOT NULL, content VARCHAR(30) NOT NULL, PRIMARY KEY(my_id(6)) ) Engine=InnoDB charset utf8mb4 collate utf8mb4_general_ci; CREATE TABLE second_table( another_id TEXT(6) NOT NULL, my_id TEXT(6) NOT NULL, another_content VARCHAR(30) NOT NULL, PRIMARY KEY(another_id(6)) ) Engine=InnoDB charset utf8mb4 collate utf8mb4_general_ci; But in the second table I can't create a foreign key that references the first table, first I've tried this:

问题 I have two tables: CREATE TABLE first_table( my_id TEXT(6) NOT NULL, content VARCHAR(30) NOT NULL, PRIMARY KEY(my_id(6)) ) Engine=InnoDB charset utf8mb4 collate utf8mb4_general_ci; CREATE TABLE second_table( another_id TEXT(6) NOT NULL, my_id TEXT(6) NOT NULL, another_content VARCHAR(30) NOT NULL, PRIMARY KEY(another_id(6)) ) Engine=InnoDB charset utf8mb4 collate utf8mb4_general_ci; But in the second table I can't create a foreign key that references the first table, first I've tried this:

问题 I have a model called Category which looks like this: class Category < ActiveRecord::Base has_many :categories belongs_to :category,:foreign_key => "parent_id" end I have a view which shows all the categories with some of their attributes. I can access category.parent_id , but I would like to be able to do something like category.parent_name . I can see myself creating a model method to fetch all categories and filling the collection with the correspondent parent name of each category, but I

问题 i have a model which is populated in a Bootstrap Modal, i am using class based view to render the form and submit it to the Database, however, when i click the save i get an error: AttributeError at /create_startupaboutform/ 'WSGIRequest' object has no attribute 'Startup' i am not sure if am assigning the FK correctly, however, for the Startup model it is working fine in function view but for class based view it is not. here is my code and i appreciate feedback on it. model.py: class Startup

问题 I'm trying to create a fk but MySQL doesn't allow it ... Identifier name 'foobarbaz_FK_CATALOG_PRODUCT_ENTITY_WEEE_DISCOUNT_PRODUCT_ENTITY' is too long [ CREATE TABLE `foobarbaz_weee_discount` ( `entity_id` int(10) unsigned NOT NULL DEFAULT '0', `website_id` smallint(5) unsigned NOT NULL DEFAULT '0', `customer_group_id` smallint(5) unsigned NOT NULL, `value` decimal(12,4) NOT NULL DEFAULT '0.0000', KEY `foobarbaz_FK_CATALOG_PRODUCT_ENTITY_WEEE_DISCOUNT_WEBSITE` (`website_id`), KEY `foobarbaz

问题 There are many questions like that but I cannot find my answer among them. Can you tell me what is wrong here? The script was created by mysql Workbench but it does not except the answer -- MySQL Script generated by MySQL Workbench -- Mon Nov 26 14:14:46 2018 -- Model: New Model Version: 1.0 -- MySQL Workbench Forward Engineering SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL

问题 I have 4 tables A(ida, name) B(ida, B-specific stuff) C(ida, C-specific stuff) D(ida, D-specific stuff) and i want that another table E could refer to just B OR C (not D). What can i write in the CREATE TABLE E ? 回答1: Seems to me that you are trying to use some kind of supertype/subtype -- as opposed to simple vertical partitioning. If so, do introduce a type-discriminator. Because this is generic example (A, B, C, D ..) it is hard to guess what relates to what, so here are two options as my

问题 I am using Spring 3.2 and hibernate-core 4.1.4 and hibernate-jpa-2.0.1. The application resource file has all the correct objects. I have a child object RoleEntity, and it has two parents: User and Award, so the userId and the awardId are foreign-keys that already exist, and MUST exist for the role entity to be created. public class RoleEntity implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "role_id") private long roleId; @Column(name = "role