relational-database

问题 I hope I'm not being too long winded in this question, I just want to make sure that what I'm asking is completely clear (I think it's rather confusing :). I've got a database with a bunch of tables with all my foreign key constraints set up. Relations are sometimes several tables deep, and there are also cases where a child is related to more than one parent table. I want to insert a copy of one of my "top level" table rows, and all of child table data that relates to it (keeping the

问题 I'm new to Hibernate and DBs in general, so pardon the elementary question. I am working with the DIS protocol and specifically the Open-DIS implementation of DIS. In DIS, each EntityStatePdu (containing the state of an entity in the simulation) has an EntityId object, a tuple of 3 integers. I want to use this object as a Natural Id, and maintain a standard surrogate ID as well. My problem is I cannot figure out how to ensure that the DB determines that a given EntityId already exists and use

问题 I have been using XAMPP for a long time and was surprised that XAMPP has switched to MariaDB from MySQL. https://www.apachefriends.org/index.html How will this change impact on existing developers using MySQL? For example, can existing development tools for MySQL work seamlessly with MariaDB? What are notable difference between MySQL and MariaDB that developers need to take note? I am not sure if it is advisable to upgrade XAMPP version because of this database change. I am worried of the

问题 I am new to influx DB. Now I need to migrate MySQL db into influxDB. I chose influx DB because it support SQL like queries. But I could not found left join in it. I have a series called statistics which contains browser_id and another series contains browser list. How can I join these 2 tables like relational database concept? I wrote this query but it is not giving any result. select * from statistics as s inner join browsers as b where s.browser_type_id = b.id statistics browsers 回答1: You

问题 I am having a problem with inserting a new row in database using Doctrine 2 and Codeigniter 2. I have two tables: languages, categories. TABLE: CATEGORIES: id, languages_id, parent_id, title Detailed table structure - http://pastebin.com/NhULaasc TABLE: LANGUAGES: id, title, slug, icon Detailed table structure - http://pastebin.com/Y6WpzdqF ENTITIES: Categories.php - http://pastebin.com/HbpKZGBL Languages.php - http://pastebin.com/vDEd60NP modelsLanguagesProxy.php - http://pastebin.com

问题 Conditions are Many teachers to one subject relationship , that is one subject can be taught by more than one teachers, but one teacher can only teach one subject Many students to many subjects relationship, that is many students can take a common subject and one student can take many subjects. Many students to many batches relationship. Two batches can not be held in one time , so need a unique date field in batch table. Many batches to one subject relationship, that is only one subject is

问题 I have one dummy table 'Users', let's call it U, and another table 'DataFromUsers', DU. From time to time i'll save a new record into DU, related to one U, and now we have 2 records pointing to the same user U. It'll come the time when i'll have lots of entries in DU resembling to this condition. The best approach i can see to solve this problem is always storing it's insertion date, once all i care is the most recent DU from U, and am only keeping the old entries for analytical purposes.

问题 When the staff change the information of product name, option name or prices. It should insert the data into history log and who done it. items table: item_id (PK) item_name item_description Note: item prices are in the item_options table item_options table: option_id (PK) item_id (FK) option_name option_price A item can have 1 or more options. If I want to change the name items.item_name , It should copy the current record to the history table, delete current record from items table and then

问题 Basically I would like to recreate this in CakePHP: Many to many relationships with additional data on the relationship or in other words, my intermediary table to have extra fields defining the type of relationship. How do I set this up in CakePHP? You can use as example: model company: id name person_id model person: id name model company_person: company_id person_id position thanx 回答1: if you want to have additional data in HABTM, use 2 hasMany relationships instead. So if A HABTM B, then

问题 I have been using following way to save dictionaries into the database: Convert the dictionary to XML. Pass this XML to a SP(Stored Procedure). In the SP use: Select Key1, Value1 into #TempTable FROM OPENXML(@handle, '//ValueSet/Values', 1) WITH ( key1 VARCHAR(MAX), value1 varchar(100) ) Done. Is there a way to save dictionaries to a database without converting it to XML? 回答1: It depends whether... You want the data to be stored: The fastest way (both implementation and performance) to do