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protogrid:database_design_fundamentals [2018-03-25 22:37] – typos, links und hierarchie druprotogrid:database_design_fundamentals [2018-03-26 07:49] (current) – [Database Design Fundamentals] 77.58.53.50
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 ====== Database Design Fundamentals ====== ====== Database Design Fundamentals ======
  
-Database design is an important task for each software developer. It is in most software development projects crucial to understand the real world problem thoroughly and be able to design the most simple database design possible. The key to success is as well a good understanding of the problem given as the ability to simplify the real world to a good model. The most talented designers master the art of designing a data model that is universal and versatile and continues to work unchanged when there will be added entities and attributes in the future.+Database design is an important task for each software developer. It is in most software development projects crucial to understand the real world problem thoroughly and to be able to design the most simple database design possible. The key to success is as well a good understanding of the problem given as the ability to simplify the real world to a good model. The most talented designers master the art of designing a data model that is universal and versatile and continues to work unchanged when there will be added entities and attributes in the future.
  
-=== Entities ===+==== Entities ====
 The real world is full of objects. If you look around you and think a bit you will find The real world is full of objects. If you look around you and think a bit you will find
   - //physical// and tangible objects like houses, dogs, cars etc.   - //physical// and tangible objects like houses, dogs, cars etc.
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 An entity is usually represented in software by a form. In table-oriented databases, an entity can also very easily be understood and represented as a table (consisting of rows and columns). In Protogrid, each entity is defined as a //[[Proto]]//, a special Design Card that is used to define the attributes, appearance and behaviour of Data Cards. An entity is usually represented in software by a form. In table-oriented databases, an entity can also very easily be understood and represented as a table (consisting of rows and columns). In Protogrid, each entity is defined as a //[[Proto]]//, a special Design Card that is used to define the attributes, appearance and behaviour of Data Cards.
  
-=== Records = Tuples = Rows = Data Cards ===+==== Records = Tuples = Rows = Data Cards ====
 Entity records have different names in literature. In table-oriented databases it is represented as a table row. More generally it is called a tuple, i.e. a set of attributes defined in an entity. In Protogrid, records are represented as //[[protogrid:card|Data Cards]]//. An entity usually has many records. Each record has a unique key that allows to identify the record. In Protogrid, that key is called a //Card Key//. Entity records have different names in literature. In table-oriented databases it is represented as a table row. More generally it is called a tuple, i.e. a set of attributes defined in an entity. In Protogrid, records are represented as //[[protogrid:card|Data Cards]]//. An entity usually has many records. Each record has a unique key that allows to identify the record. In Protogrid, that key is called a //Card Key//.
  
-=== Attributes = Fields = Columns ===+==== Attributes = Fields = Columns ====
 An entity has attributes. Each attribute describes a part of the entity. In table-oriented databases, an attribute is represented as a table column. In Protogrid, attributes are represented as //[[protogrid:field|fields]]// on a Data Card, and are defined using //Field Definitions// on the Proto. Field Definitions are another type of Design Card, responsible to define the behaviour and appearance of fields. An entity has attributes. Each attribute describes a part of the entity. In table-oriented databases, an attribute is represented as a table column. In Protogrid, attributes are represented as //[[protogrid:field|fields]]// on a Data Card, and are defined using //Field Definitions// on the Proto. Field Definitions are another type of Design Card, responsible to define the behaviour and appearance of fields.
  
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   * etc.   * etc.
  
-=== Relations ===+==== Relations ====
 Often there are **relations** between entities. Often there are **relations** between entities.
  
-== The 1:n-relation (Mother-Child Relations) ==+=== The 1:n-relation (Mother-Child Relations) ===
 For one mother there might be many, one or no child. We call this a 1-to-many-relation and write 1:n, with //n// representing the variable number of children. //1// and //n// are often called the //cardinality// of an entity in a relationship. In database design, the variable //n// is usually repeated for each of the relations, even though each represents the cardinality of a different entity. For one mother there might be many, one or no child. We call this a 1-to-many-relation and write 1:n, with //n// representing the variable number of children. //1// and //n// are often called the //cardinality// of an entity in a relationship. In database design, the variable //n// is usually repeated for each of the relations, even though each represents the cardinality of a different entity.
  
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 This knowledge is already enough to build many different types of applications. This knowledge is already enough to build many different types of applications.
  
-= How to implement 1:n-relations in Protogrid =+== How to implement 1:n-relations in Protogrid ==
   - create the [[Proto]] for the child entity   - create the [[Proto]] for the child entity
   - create the Proto for the mother entity   - create the Proto for the mother entity
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 There is one more important variant of relations: There is one more important variant of relations:
  
-== The n:m-relation ==+=== The n:m-relation ===
  
 Sometimes a child has not only one related entity (like a mother - there is only one for each child on this planet) but many. The closest example to think of are siblings. Sometimes a child has not only one related entity (like a mother - there is only one for each child on this planet) but many. The closest example to think of are siblings.
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-=== Summary ===+==== Summary ====
   * Entity ~ form ∼ table ~ Proto   * Entity ~ form ∼ table ~ Proto
   * Record ~ row in a table ~ Data Card   * Record ~ row in a table ~ Data Card
   * Attribute ~ column in a table ~ field   * Attribute ~ column in a table ~ field

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