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mysql workbench tables inheritance

MySQL does not support table inheritance. The only way to approximate the functionality is by using a foreign key (which MySQL isn't too. What I am wondering is how a multiple inheritance MWB would look like? So in order to get such a Class Table Inheritance we would need to have in MWB. Suppose I have equipment_parent_id = 1, 2, 3, 4, etc., I don't want to query all the children tables (tank, piping, etc) to find which one has. LOGITECH QUICKCAM ZOOM V UW21 DRIVERS DOWNLOAD Mysql workbench tables inheritance cisco ios software packaging for cisco catalyst 6500 series

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Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search. I'd like the ERD to look similar to the left side of this image:. Yes, I tried first with sybase Connect Footballer and Player.

It will give you name as primary key and foreign key. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 12 years ago. Modified 4 years, 10 months ago. Viewed 4k times. Improve this question. Matt Norris Matt Norris 7, 11 11 gold badges 54 54 silver badges 88 88 bronze badges. Add a comment. Ask Question. Asked 7 years, 5 months ago.

Modified 7 years, 5 months ago. Viewed 9k times. Improve this question. Add a comment. Sorted by: Reset to default. Highest score default Date modified newest first Date created oldest first. Improve this answer. Patrick Patrick PostgreSQL inheritance is not SQL-compliant, for instance, and not all constraints are inherited so one should be really careful when working with inheritance. Unless you really need inheritance for some data model reason you are probably better off with a standard relational structure.

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Databases: How to model inheritance of two tables MySQL? (4 Solutions!!)

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When designing a database, we sometimes come across situations where there are multiple types of entities that we are modeling, but we'd like them to all have certain attributes or relations in common. Using "sub-type" tables is a simple way to implement table inheritance in SQL Server. For example, a question came up recently about modeling the following entities in a "School" database:. Each of those entities has many of the same attributes, such as first name, last name, middle name, and birth date.

Yet, we must separate them into multiple tables because we need to store and track different data for students, teachers and parents: students have grades and classes and parents; teachers have classes taught, skills, employment information, and so on. In addition to sharing common attributes, these entities also have common relations. For example, for each of those entities we might also like to store addresses, phone numbers, correspondence history, etc.

To do this in a nicely normalized database, we would model that data by creating additional tables:. Yet, again, we need different tables for these different entities because they each have their own set of relations and attributes to track. Is there an easier way to model this in a relational database?

Absolutely -- let's take a look. We can start by recognizing that Students, Teachers, and Parents are all "People", and we can note that it makes sense to say that all People can have addresses and phone numbers and correspondence history:. In the People table, we'd store all of the common attributes of Students, Teachers and Parents that we discussed earlier: name, birth date, and so on.

We remove all of these common columns from the Students, Teachers and Parents tables and put them all in one place. Now, maintaining phone numbers, addresses, names, birthdays, and correspondence can all be done with one set of generic stored procedures. The redundancy of those activities has now been reduced, and any changes in phone number or address formats can all be done in place.

We can refer to the People table as a "base table". Of course, we still need our Students, Teachers and Parents tables -- but now the primary key of these tables also becomes a foreign key to the People table. Because any row in the Students, Teachers or Parents tables require a related row in the People table, and it also shares the same primary key as the People table i.

Think of these sub-tables as tables that extend the basic information that the People table provides; this is similar to how inheritance works in Object-Oriented Programming OOP. Essentially, we are performing "table inheritance" by doing this; since every student, teacher and parent is by definition also a "person" and we are guaranteed that we can work with all of those entities the same way by treating them as People if we want, or we can work with them using their specific attributes and relations.

That 3rd point is important, as it may not be what you want; we'll get back to that in a moment. But for our purposes, I think it makes sense: suppose a person is initially a student, comes back to work for the school as a teacher, and then eventually has kids of their own. This schema allows us to handle that. The 4th point is important to consider as well. We could add a "PersonType" column to the table, and create a table of PersonTypes -- but then we introduce redundancies and the possibility of conflicting data.

Also, as mentioned, a person can be more than one "type" at a time, so the existence of this column doesn't really make sense in this table without changing our logical model. Using this schema is easy; we can quickly get all of the information for all of the students with a simple join:.

So, everything works beautifully. We have our base table, we have our sub-tables, and the inheritance allows us to work with the different entities all the same way, but to also treat each of them specifically on their own as necessary. However, what if we want to set up our model so that a Person can have only one type; i.

This is a more accurate database implementation of inheritance, since in OOP you cannot create an instance of something that is more than one sub-class at a time -- you must pick one or the other or potentially the base class itself, if that's what you need. Modeling this can be tricky, and it can be done a couple of ways. This is the table that defines the different types our system will allow. There will be one entry in this table per "sub-table" that we create.

If we want to allow for a Person to be just a generic "Person" without any specify sub-type, we could add a row for "Other". With that table in place, we will now add a PersonType column to our People table. Pretty standard stuff so far — we have different types of People we are modeling, and each Person must be assigned a type. And now comes the trick: We will add an extra PersonType column to each of our sub-tables, and force the value in that column to be equal to the PersonTypeID for that table.

In SQL , we can just add a default and a check constraint, but in SQL we can use a persisted computed column. So, our Students table will have a constant PersonType value of 1, the Teachers table a value of 2, and the Parents table a value of 3. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow.

Learn more. Does MySQL support table inheritance? Ask Question. Asked 7 years, 5 months ago. Modified 7 years, 5 months ago. Viewed 9k times. Improve this question. Add a comment. Sorted by: Reset to default. Highest score default Date modified newest first Date created oldest first. Improve this answer. Patrick Patrick PostgreSQL inheritance is not SQL-compliant, for instance, and not all constraints are inherited so one should be really careful when working with inheritance.

Unless you really need inheritance for some data model reason you are probably better off with a standard relational structure. Sign up or log in Sign up using Google. Sign up using Facebook.

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