foreign-keys

问题 I created table with FOREIGN KEY and can't insert anything. CREATE TABLE menus ( id int(10), parent_id int(10), label varchar(255), PRIMARY KEY (id), FOREIGN KEY (parent_id) REFERENCES menus (id) ); I need FOREIGN KEY to automatically delete children when parent was deleted. This table was successfully created but I can't insert anything. INSERT INTO `menus` (`parent_id`, `label`) VALUES ('1', 'label1'); or INSERT INTO `menus` (`label`) VALUES ( 'label1'); #1452 - Cannot add or update a child

问题 Since foreign keys are not supported by partitioned mySQL databases for the moment, I would like to hear some pro's and con's for a read-heavy application that will handle around 1-400 000 rows per table. Unfortunately, I dont have enough experience yet in this area to make the conclusion by myself... Thanks a lot! References: How to handle foreign key while partitioning Partitioning mySQL tables that has foreign keys? 回答1: Well, if you need partitioning for a table as small as 400.000 rows

问题 We use event sourcing with SQL Server 2016. We have total Customer Product Application, each is labelled by CustomerId and gets a single Guide line item in the event store. This is the primary identifier for write event store guids. The Product Applications comes with many different relational things, (which do not have guids but natural keys) each customer has Multiple Addresses, Accounts, Multiple purchase orders. The write event store will be mapped to a relational database tables any way

问题 OK so now I can understand that SO's search system is primarily based around tags, the tag system they use is a very good one at that but what I want to do is replicate it for my own projects. Now I can understand how to use foreign keys and such, but I'm not exactly sure how it's been developed here, do they use 3 tables or 2 etc. How have they developed it, can you show me some MySql examples? 回答1: SO considers questions and answers to be the same thing - a Post . Here's a stripped down

问题 I have such structure of db http://pikucha.ru/icFsc (I can't add pictures here) Some addresses my not have a metro (other tables have the same problem, for example "user" may not have an address, but there is constraint in "user" table) If I add a record in mysql it's ok. If I do the same thing using yii I get an error Cannot add or update a child row: a foreign key constraint fails ( address , CONSTRAINT fk_Address_Area1 FOREIGN KEY ( area_id ) REFERENCES area ( id ) ON UPDATE NO ACTION) So,

问题 i'm trying to build a mini reply system, based on the user's posts on a mini blog. Every post has a link named reply. if one presses reply, the reply form appears, and one edits the reply, and submits the form.The problem is that i don't know how to take the id of the post i want to reply to. In the view, if i use as a parameter one number (as an id of the blog post),it inserts the reply to the database. But how can i do it by not hardcoding? The view is: def save_reply(request): if request

问题 I have two foreign keys in an entity refering to another entity. Here is how it looks class Review(db.Model): __tablename__ = 'Review' id = db.Column(db.Integer, primary_key = True) user_id = db.Column(db.Integer, db.ForeignKey('User.id'), nullable=False) business_user_id = db.Column(db.Integer, db.ForeignKey('User.id'), nullable=False) user = db.relationship('User', foreign_keys=[user_id]) business_user = db.relationship('User', foreign_keys=[business_user_id]) and class User(db.Model): _

问题 I am trying to insert primary and foreign keys in XSD schema file below :- Primary key is StudentID and Foreign Keys are courseID, AddressID, GradeID. <?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="Student"> <xs:complexType> <xs:sequence> <xs:element name="Title" type="xs:string"/> <xs:element name="FirstName" type="xs:string"/> <xs:element name="LastName" type="xs:string"/> <xs:element name="Dateborn" type="xs:date"/> <xs:element name="Gender"

问题 I have an existing InnoDB table which already has foreign keys pointing to different tables. But when I try to create a foreign key pointing to the Primary index, I get an error (check data type). The table is User with User_Id as the Primary. I want a foreign key Manager_ID which is a FK to User_Id. Both of INT Both of Length 10 Unsigned... But I still get a data check error...? 回答1: Make sure that Manager_ID is not set to NOT NULL . You have to allow nulls on that field, as the top-most

问题 What algorithms are known to perform the task of updating a database by inserting, updating, and deleting rows in the presence of database constraints? More specifically, say that before images of rows to be deleted, after images of rows to be inserted, and both images of rows to be updated are in memory. The rows might be for several tables. An exact sequence of updates is either not known or has not been preserved -- only the before images and the after images that the database must