entity-relationship-model

Error 1005 when Forward Engineering EER diagram

由 南楼画角 提交于 2020-01-15 07:30:07
问题 I have created an EER diagram (as shown in the image bellow) in MySQL Workbench and wanted to Forward Engineer to build the DB. After configuring the model options to the Target MySQL Version and removing the word "Visible" from all the Indexes in the SQL Code (the code goes in the bottom of this post), as it was triggering an error, I have came across a 1005 Error: Executing SQL script in server ERROR: Error 1005: Can't create table `books`.`books` (errno: 150 "Foreign key constraint is

in a relational database, can we have a table without any relation with the other tables?

由 孤街醉人 提交于 2020-01-11 05:16:09
问题 in a relational database, can we have a table without any relation with the other tables? 回答1: Yes. The way relations are expressed are with foreign keys. If a table you generate has no Foreign keys, and no foreign keys in other tables point to this table, it has no relationships. It can still be given a relationship later though so don't worry about shooting yourself in the foot. 回答2: Of course. Even you can create a table without fields. 回答3: Yes you can. Tables do not have to have any

Creating an entity relationship diagram

由 别说谁变了你拦得住时间么 提交于 2019-12-25 14:40:14
问题 I've created this ERD: But now I want to add some more information to my diagram, but I do not how I should do that. I want to modify my previous ERD, I need to register what recipe was made by what chef in each program. Also, I want to identify what ingredient and tool were used in each step of the recipe. 回答1: I think implementing your Entity Relationship Diagram into Microsoft Access can be a good start. You've clearly defined the relations between each entity and have declared attributes

Relationship in ER model

由 走远了吗. 提交于 2019-12-13 06:59:51
问题 I am learning about ER modelling about Database systems. My problem is that there is a entity called books,enitity named user and I want to create a borrows relationship between user and book with attribute issue date. I modelled it as described but it was pointed that borrows cannot be a relationship because a same user can borrow a book twice. Can anybody explain me what this is as I am using issue data as an attribute so records in borrows relationship would not collide as I will use PK as

What is the right way to use Associative Entity?

由 。_饼干妹妹 提交于 2019-12-13 03:11:23
问题 This is the description: Draw an Entity-Relationship diagram for Poke-Hospital which provides medical service to pokemon. Each pokemon has an appointment with one of the nurse Joys. In addition to recording the name, type and trainer of each pokemon, the system needs to keep track of the multiple types of sickness being diagnosed for the pokemon. During an appointment, the nurse will always prescribe medicine. It is required to record the date, time and dosage of the medicine. A pokemon may

How to do json format using nltk

由 99封情书 提交于 2019-12-12 03:28:16
问题 How to do json format using nltk. Example: tagged_sent = [('Rami', 'PERSON'), ('Eid', 'PERSON'), ('is', 'O'), ('studying', 'O'), ('at', 'O'), ('Stony', 'ORGANIZATION'), ('Brook', 'ORGANIZATION'), ('University', 'ORGANIZATION'), ('in', 'O'), ('NY', 'LOCATION')] I want output like json format: data = { 'Rami Eid':{'job': 'engineer', 'location':'NY'}, 'GuruRaj Bagali':{'job': 'professor', 'location': 'NY'} } 来源： https://stackoverflow.com/questions/35178585/how-to-do-json-format-using-nltk

How to know relations between tables

由 ☆樱花仙子☆ 提交于 2019-12-06 16:54:18
问题 I have a database in MySQL created by someone. I don't have any documentation of the database. How can I know the relationship between the tables? Is there any query or a procedure to generate a report so that it's easy to find the relations? I can look into Schema information and manually figure it out, but it would be great if I could generate a relationship report. 回答1: The better way as programmatically speaking is gathering data from INFORMATION_SCHEMA.KEY_COLUMN_USAGE table as follows:

How to know relations between tables

由 大城市里の小女人 提交于 2019-12-04 22:38:50
I have a database in MySQL created by someone. I don't have any documentation of the database. How can I know the relationship between the tables? Is there any query or a procedure to generate a report so that it's easy to find the relations? I can look into Schema information and manually figure it out, but it would be great if I could generate a relationship report. The better way as programmatically speaking is gathering data from INFORMATION_SCHEMA.KEY_COLUMN_USAGE table as follows: SELECT `TABLE_SCHEMA`, -- Foreign key schema `TABLE_NAME`, -- Foreign key table `COLUMN_NAME`, -- Foreign

What are the basic rules for defining entities, attributes, and relationships in an ER-Diagram?

由 回眸只為那壹抹淺笑 提交于 2019-12-02 15:55:51
问题 My question is: In order to exist which of the following needs obligatory to have key and attribute? entity entity-type relationship-types relations (tuple with relationship-types) I know my question is a little bit odd, but I am not quite sure what are the rules by building an ER-Diagram. In other words what should mandatory be present in my diagram and what not (e.g Attributes). Thanks in advance. 回答1: In the original Entity-Relationship method, we identfy entity types and relationship

What are the basic rules for defining entities, attributes, and relationships in an ER-Diagram?

由 十年热恋 提交于 2019-12-02 09:55:26
My question is: In order to exist which of the following needs obligatory to have key and attribute? entity entity-type relationship-types relations (tuple with relationship-types) I know my question is a little bit odd, but I am not quite sure what are the rules by building an ER-Diagram. In other words what should mandatory be present in my diagram and what not (e.g Attributes). Thanks in advance. In the original Entity-Relationship method, we identfy entity types and relationship/association types and their relevant attributes. When drawing an ER diagram we pick one or more groups of
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