The IF NOT EXISTS is an optional clause of the statement. The IF NOT EXISTS clause prevents you from an error of creating a new database that already exists in the database server. You cannot have 2 databases with the same name in a MySQL database server.
Table does not have to have primary key. ... Even if you do not add a primary key to an InnoDB table in MySQL, MySQL adds a hidden clustered index to that table. If you do not define a primary key, MySQL locates the first UNIQUE index where all the key columns are NOT NULL and InnoDB uses it as the clustered index.
Every table can have (but does not have to have) a primary key. The column or columns defined as the primary key ensure uniqueness in the table; no two rows can have the same key.
No. Every table should have some column (or set of columns) that uniquely identifies one and only one row. It makes it much easier to maintain the data. It's true, without a primary key (or some unique key), you don't have an insertion anomaly if you go to insert the same data multiple times.
Every table can have (but does not have to have) a primary key. The column or columns defined as the primary key ensure uniqueness in the table; no two rows can have the same key. The primary key of one table may also help to identify records in other tables, and be part of the second table's primary key.
A table can have only one primary key, which may consist of single or multiple fields. When multiple fields are used as a primary key, they are called a composite key. If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).
Every entity in the data model shall have a primary key whose values uniquely identify entity instances. The primary key attribute cannot be optional (i.e., have null values).
A weak entity is one that can only exist when owned by another one. For example: a ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a strong entity because it also can exist without being attached to a CAR. Just to play with it, question is strong entity type and answer is weak.
Sometimes more than one attributes are needed to uniquely identify an entity. A primary key that is made by the combination of more than one attribute is known as a composite key. ... It may be a candidate key or primary key. Columns that make up the composite key can be of different data types.
The primary key is a candidate key that is selected by the database designer to be used as an identifying mechanism for the whole entity set. It must uniquely identify tuples in a table and not be null. The primary key is indicated in the ER model by underlining the attribute.
Cardinality can be 1 or Many and the symbol is placed on the outside ends of the relationship line, closest to the entity, Modality can be 1 or 0 and the symbol is placed on the inside, next to the cardinality symbol. For a cardinality of 1 a straight line is drawn.
Below points show how to go about creating an ER diagram.
ER Diagram stands for Entity Relationship Diagram, also known as ERD is a diagram that displays the relationship of entity sets stored in a database. ... ER Diagrams contain different symbols that use rectangles to represent entities, ovals to define attributes and diamond shapes to represent relationships.
What are the Types of ERP Systems?
Entity Relationship Model (ER Modeling) is a graphical approach to database design. It is a high-level data model that defines data elements and their relationship for a specified software system. An ER model is used to represent real-world objects. ... For example, each employee of an organization is a separate entity.
Enterprise resource planning (ERP) is a process used by companies to manage and integrate the important parts of their businesses. ... An ERP software system can also integrate planning, purchasing inventory, sales, marketing, finance, human resources, and more.
ERP software is a large suite of integrated applications that manage everyday business processes and automate back office functions. ... For example, in the supply chain industry, an ERP system could automatically run a financial analysis and predict future stock needs to keep inventory at a healthy level.
Heart of an ERP comprises of its central database.
While the entire organization will come to rely on both ERP and CRM systems, the fundamental difference between ERP and CRM is that ERP is primarily for financial data and the finance department, while CRM is customer data used by the sales and customer service departments.
Popular ERP vendors like Epicor, SAP, and Microsoft either also make CRM software, or their ERP solutions directly integrate with CRM from other vendors.
NetSuite software is an online service that enables companies to manage all key business processes in a single system. ... Companies use NetSuite for enterprise resource planning (ERP) and to manage inventory, track their financials, host e-commerce stores and maintain customer relationship management (CRM) systems.
As part of ERP, CRM is one of the five ERP pillars, with the other four pillars being financial accounting, distribution or supply chain management, manufacturing and human resources/payroll. ... CRM has a central database and integrates with an ERP system and different channels of interaction.
CRM (Customer Relationship Management) and ERP (Enterprise Resource Planning) software are powerful tools for a business or enterprise to use. CRM handles the sales, marketing, and customer service information. ... On the other hand, manufacturing ERP handles the back-end processes and internal information.
ERP are software solutions that helps organizations to manage their business processes. SAP is multinational company that sells ERP software solutions to business. ... It is a centralized system that streamline all processes. It groups process into modules and interact with different business aspects.
The biggest difference between MRP and ERP lies in the fact that MRP is more of a solo software, while ERP is integrated. This means that ERP can easily connect to other software systems and modules. ... On the other hand, MRP systems are standalone and function by themselves with only manufacturing-related tools.
ERP stands for Enterprise Resource Planning. ... Depending on the definition, there are two possible interpretations for an MRP system - Material Requirement Planning (MRP) and Manufacturing Resource Planning (MRP System II), which eventually developed into ERP.