Instructor: Jing Gong

Weekly Question #3 (Due Friday, September 18)

Leave your response as a comment on this post by the beginning of class on September 18, 2015. Remember, it only needs to be three or four sentences. For these weekly questions, I’m mainly interested in your opinions, not so much particular “facts” from the class!If you sign in using your AccessNet ID and password you won’t have to fill in the name, email and captcha fields when you leave your comment. Answer one of the two questions below (not both):
  1. Describe a situation where you could use a join to retrieve information from a set of tables. For example, if you have orders in one table and customers in another table, you’d need to join those tables to figure out which orders were placed by the customers who lived in Pennsylvania.
  2. Name one difference (there are more than one) between an ERD and a schema.

42 Responses to Weekly Question #3 (Due Friday, September 18)

  • A database schema uses tables instead of a diagram. Most of the work is based off a table where the data is entered. On the other hand, ERD’s are more of a visualization between tables in a database. Basically, the difference between the two is that schema inpus data into an actual table while a ERD is a visualization of those tables in the form of a diagram.

  • A database schema uses tables instead of a diagram. Most of the work is based off a table where the data is entered. On the other hand, ERD’s are more of a visualization between tables in a database. Basically, the difference between the two is that schema inputs data into an actual table while a ERD is a visualization of those tables in the form of a diagram.

  • The main difference between an ERD and a schema is how it looks. An ERD is a data model that describes the data and information by using entities, attributes, relationships, and cardinalities. An ERD draws a picture of how each entity and attribute is linked to each other. A schema is a series of tables linked through primary and foreign keys. A schema is created from using the information of an ERD which includes an additional table in which links one entity to another.

  • I believe the biggest difference between and ERD and Schema is the table formats. One table is visual which is the ERD where things are displayed visually with boxes and triangles. However, a Schema displays things in a data table which is less visual and more analytical. That’s the major difference in my opinion between the two.

  • A difference between an Entity Relationship diagram and a database schema is that the ERD diagram is a visual representation of the relationships between entities and tables in a database where schema is a description of the actual construction of a database. Schema does not portray any visual representation of the database relationships, entities, or attributes. Schema includes tables with rows and columns rather than diagrams.

  • There are many differences between ERD’s and schemas. Schemas is a description of the database and refers to the collective tables, columns, relationships, procedures and some more. While ERD’s is a visualization of the relationship between of the database and is represented with shapes as entities and attributes.

  • A difference between an ERD and a schema relates to the joined tables used in schemas. An ERD does not explicitly distinguish when a relationship creates a joined table. For instance, you can only represent a relationship between two entities with a diamond shape. You cannot use a hexagonal shape to define which relationships require joined tables in a schema. You have to infer which entities’ relationships require joined tables by referring to the cardinality between those two entities.

  • The main difference between ERD’s and schemas is that an ERD is the visualization of the relationship between databases and tables and a schema is the actual database construction.

  • The difference between a ERD and a Schema is that an ERD is more of a picture of the relationship between the different tables while a Schema is the actually description of the database. The schema is the tables being connected while the ERD is the tables as shapes and connected. Both are equally effective but is up to the discretion of the user.

  • One difference between an ERD and a Schema is a schema is the actual database, as where the ERD is only a diagram indicating abstract concepts and relationships between databases.

  • One difference between ERD and schema is that the many-to-many relationship is illustrated differently in both. In ERD, many-to-many relationship is expressed by buying the crow feet notation on both tables. While the many-to-many relationship in a schema is expressed by creating a separate table where its name is the name of both tables in the relationship combined.

  • Using join to retrieve information from a set of tables can be utilize in many areas of business, especially in the shipping industry. I experienced this idea of pairing and matching customers with items in a table while working with an International Shipping company. When products come in from overseas they are only allocated with a shipping invoice; product Id, invoice number, destination of origin, and quantity. When the shipment is receive in the warehouse it they match the invoice number to another log which will match it to the customer who will receives the product. This matching allows for the product to travel the course to help assure the product gets to its assigned destination. With this system it helps to eliminate errors and reduce the amount of information that has to be passed from point “A” to “B”.
    Best GJR

  • Schema and ERD may seem confusing because have contain a lot of the same information but they are both applied in different ways. A schema is the description of the actual build-up of the of the database. The ERD is a diagram that shows the relationships between entities and their attributes within a database.

  • One difference between an ERD and a schema is that an ERD tries to reduce the redundancy as much as possible while a schema can have some overlap when being created. For example an ERD that has a many to many relationship between different entities still remains as a separate entity. When a schema is created that involves a many to many relationship between different entities, an new table is created between the different entities that combines the two into a combination table. For example, a many to many relationship between customers and products would result in a new table called customer-product which would result in their being redundancy in the attributes for the tables with repeated primary keys. However, this redundancy allows for the user to find the relationship between various entities more easily.

  • The difference between a Schema and ERD is: Schema is a database that will set up a system to retrieve other information out of the database. The ERD system is an actually diagram to connect important information.

  • One situation where you could use a join to retrieve information from a set of tables is if you have units on one table and tenants of those units on another table. You would then join the two tables to figure out which tenant lives in a certain unit.

    One difference between an ERD and a schema is that in an ERD a relationship cannot become an additional table. In a schema relationships can become additional tables.

  • The difference between an ERD and a Schema is an ERD is a visual relationship between tables in a database. A schema is a description of the construction of the database. A schema is a map of tables and fields, where entities are tables and attributes are fields.

  • Although there are multiple differences between an ERD and a schema, one difference is that the schema is the table/list of items being displayed in the ERD diagram itself. The ERD diagram simply puts the tables into a connected, drawn out fashion, making it easier to visualize. The inputs for the schema directly correlate to the visual of the ERD diagram. For instance, I would type out all of the entities and attributes in a table for the schema, and then display/show how they connect on an ERD diagram.

  • 1. One situation where you would have to join the tables would be if you had appartment unit information in one table and resident information in another table. If you wanted to find out which customers live in units with 2 or more bathrooms you would have to join the tables.

    2. One difference between an ERD and a schema is that an ERD shows the relationships between entities and attributes in a more broad way while schemas are more visually focused on showing the relationships between the primary keys and the entities.

  • Joining tables for orders and customers would be very helpful in a situation where you were running an online retail business and wanted to track the effectiveness of a new marketing initiative. If this company was testing a new way of marketing a product in one of its regions, having the ability to track sales for that specific region would allow management to see what type of return the new marketing plan is bringing to the company.

  • the difference between an ERD and a Schema is that Schema needs to create one more table when its many to many relationship

  • An ERD is a outline/layout of the relationships between the different tables in a database. It is represented with squares and lines that connect one another with a relationship. A Schema is a collection of database objects associated with one particular database username. This means that in a database anyone can create their own schema and will have certain privileges in the database.

  • An ERD and a schema are very similar in the way that they are composed, however they are used in many different ways. They are both groupings of information but schemas are lists mainly based on customer order-product information and how they are related and searched. Where-as an ERD is a representation diagram of the information and how it is displayed for it to be searched.

  • One of the differences between an ERD and a schema is that, when building relationship of a many to many relationship, the relationship becomes an additional table to connect one table(entity) to another. This really makes it easier for database users to sort out data and their relationships without redundancy. If a database is a maze, the ER diagram is like showing you this “maze” looks like, but a schema will navigate the location you want in this ”maze’.

  • A situation where I would need to use join to retrieve information from a set of tables is if I am running a gym and need to know which one of my employees are certified in CPR/AED, and since they are 2 years certifications, I would need to know which ones are expiring.

    ERDs are visualizations of data diagrams whereas schemaare the collection of the tables and data, and columns.

  • one difference between an ERD and a schema is that ERD is more of a visual type of data that relates to tables in a database. ERD contains a header for the table. Schema is the foundation of the database where it can be unorganized

  • 2. The main difference between a schema and an ERD is that a schema is more used to describe how a particular database was constructed while an ERD is more of a visualization of how the tables in a database are related to one another. Essentially, a key factor is that a user can simply insert more data into an existing schema while an ERD serves more of a visual purpose. The schema is generally the storage facility for the information while the ERD serves the purpose of identifying how the tables hold a one-to-one, one-to-many, or –many-to-many relationship.

  • The difference between ERD and schema is the visual presentation of the data and relationships. ERD are presented like a flow chart showing how the data are related. Schema are presented in tables and fields, which use in databases because it’s a simpler version of ERD. ERD are presented in very detailed, while schema are presented simpler.

  • Name one difference (there are more than one) between an ERD and a schema. An ERD is a visual representation showing the relationships while a schema is an actual description/ representation of the relational database.

  • The difference between an ERD and schema is the way they look. In an ERD, we use three main elements: entities, relationships and attributes to create a model/diagram. To create the entity-attribute-relationship, we use rectangles, diamonds and ovals. A schema shows the structure of the data organized in tables, whereas an ERD visually outlines the information in the schema using shapes.

  • ERD and schemas have similarities and differences. One difference between ERD and schemas is the composition of data being displayed. Both of the two consists of elements such as entities, attributes, and relationships. However, an ERD is a relational diagram that use shapes to display the visualization of those elements. On the other hand, schemas use multiple tables connected to fields to describe the relationship between these elements.

  • I believe I am correct in saying that ERD diagrams show a basic relationship between the tables in a database, including the relationships between the tables or “entities” and also showing their attributes. Based on the lecture slides so far, a schema appears to be a description of the actual database and its functionality. Simply, an ERD diagram is an abstract concept whereas a schema is not; it is the actual database.

  • Name one difference (there are more than one) between an ERD and a schema.

    The difference is that a schema can make +1 table. It means, If there are two schema in m:n relationship, These two table creates one table which contain foreign keys. So when you look at ERD, you not only have to look at the entities and attribute, but also you have to check the cardinality so that you don’t miss the table.

  • One difference between ERD and schema is that schema is the actual database, while ERD is a diagram illustrating the connections between relationships, entities and attributes. An ERD diagram can be used as a basis to model a schema. The schema can be used to actually retrieve specific information.

  • An ERD is a visualization of entities and attributes which shows the kind of relationship happening. It can be used to define the process going on. A schema is a model that you put data into rather than using it to see the relationships.

  • One difference between ERD and schema is that ERD have entities and attributes and schema have tables and fields. The biggest difference I think is that schema can have a join which allows for more information about any field by joining any number of tables. The join makes it easier to find out more information and is only offered in schemas because they use tables while ERD use entities.

  • The main idea in an ERD is to show the relationships between the different entities. Once the ERD is completed, it is used to create a schema. A schema is used to help design the database, while an ERD is created to show relationships and help create a schema.

  • They are different since data schema is description/blueprint of the construction of a database,while an ER model is shows the relationships between tables in a given database.

  • A schema describes the construction of a database, and is typically all encompassing but does not include the actual data in the database. On the other hand, and ERD is simply a visual representation between the relationships of the tables in the database. Additionally, a schema is based on an ERD so they are closely related.

  • With regard to a dimensional paradigm, a merchant will want to structure their store(s) schema in collusion with their product(s) and time, relative to sales. Therefore, the merchant may want to join sales via an associated order’s primary key (say, customer ID #) to the specific customer’s customer ID # in its own table. For example, if a financial services firm seeks to track demand metrics for its various products, it may set a “sniffer” function up to correlate common background information on investors and then further isolate them by possibly geographic region or some other appropriate attribute(s). A retail firm may join customers in respective regions (based on billing address and customer ID, if they have ongoing accounts with the firm) with, say, a particular store ID #. In the analytical data store, this subjective grouping would facilitate data mining more expediently, since the database is more efficiently navigated. The cardinality would be likely be 1:many for each store ID # to isolate a specific query. Perhaps an automated ‘COUNT’ query, using SQL, could take on the burden of tabulating the necessary in-common metrics between investors (or retail customers).

    One difference between and ERD and its respective schema would be an entity in a schema table would have an additional entry that matches an attribute in a neighboring table to establish a necessary ‘join’ between the two. In an ERD, each entity is flanked by its particular attributes and linked via defined cardinality to show the flow of data in the ERD.

  • An Entity Relationship Diagram, also called an ERA, is a chart that shows the relationships between tables in a database. This allows people to visualize the relationships. While a schema shows what the actual database looks like by. It shows links between the tables that make up the database.

  • Question 2- A schema is a description of the construction of the database. It refers to the relationships. You insert data into a schema. An ERD diagram is a visualization of the relationships between tables in a database. It includes column names and symbols that include information about what kind of relationship exists between the columns.

  • A database schema is usually a relational model/diagram. it shows the link between tables: primary keys and foreign keys. In database diagram the relation between an apple and a apple tree would be: A foreign key “ID__TRE” which cannot be null in the table “APPLE” is linked to a primary key “ID_TRE” in the table “TREE”.

    An entity relationship diagram. Shows links between the entities and the kind of relation between them. We are not talking about tables or keys there! Usually the entity relationship diagram follows Merise model. Database manager and developer as myself usually build an entity relationship model before conceiving the relational model/diagram.

  • A schema is basically a table of the the database you are creating that can also include things such as relationships and functions. An Entity Relationship Diagram is more of the visual representation of the schema. It includes the table names displayed in entity squares and are connected to attributes. The difference is the visual aspect. The names are connected and represent relationships among each other to show the data more clearly.

  • 1. There are endless situations that occur in which using a join to retrieve information from a set of tables is useful. SQL is powerful software that enables efficient intelligence gathering from databases. Business owners need to know the departments in which specific employees work. This problem is solved when a table containing employee names is joined with a table containing departments.

  • One difference between an ERD and a schema is that schemas only show maximum cardinality, as having both maximum and minimum cardinality isnt necessary for the change in format.

  • A difference between an ERD and and a schema is the visual representation. An ERD shows the relationship between attributes and entities by giving them a square or circle shape. and the relationship between entities are shown by diamonds. A schema though shows the relationship between tables by connecting them to foregin keys located in their fields.

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