Hierarchical database model - Wikipedia
Definition. The parent-child relationship consists of a combination of however, a firstborn or an only child, who has no example to watch, may not excel in other . A Quick-Start Tutorial on Relational Database Design Gather the requirements and define the objective of your database, e.g.. For example, an unique number customerID can be used as the primary key for the . A foreign key of a child table is a primary key of a parent table, used to reference the parent table. In this model, the employee data table represents the "parent".
A table is made up of rows and columns. A row is also called a record or tuple. A column is also called a field or attribute. A database table is similar to a spreadsheet. However, the relationships that can be created among the tables enable a relational database to efficiently store huge amount of data, and effectively retrieve selected data.
Database Design Objective A well-designed database shall: This is because duplicate data not only waste storage spaces but also easily lead to inconsistencies. Ensure Data Integrity and Accuracy: Databases are usually customized to suit a particular application. No two customized applications are alike, and hence, no two database are alike.
Guidelines usually in terms of what not to do instead of what to do are provided in making these design decision, but the choices ultimately rest on the you - the designer. Define the Purpose of the Database Requirement Analysis Gather the requirements and define the objective of your database, e. Drafting out the sample input forms, queries and reports, often helps. Gather Data, Organize in tables and Specify the Primary Keys Once you have decided on the purpose of the database, gather the data that are needed to be stored in the database.
Divide the data into subject-based tables.
Choose one column or a few columns as the so-called primary key, which uniquely identify the each of the rows. Primary Key In the relational model, a table cannot contain duplicate rows, because that would create ambiguities in retrieval.
To ensure uniqueness, each table should have a column or a set of columnscalled primary key, that uniquely identifies every records of the table. For example, an unique number customerID can be used as the primary key for the Customers table; productCode for Products table; isbn for Books table.
A primary key is called a simple key if it is a single column; it is called a composite key if it is made up of several columns.
The primary key is also used to reference other tables to be elaborated later. You have to decide which column s is to be used for primary key. The decision may not be straight forward but the primary key shall have these properties: The values of primary key shall be unique i.
For example, customerName may not be appropriate to be used as the primary key for the Customers table, as there could be two customers with the same name.
The primary key shall always have a value. In other words, it shall not contain NULL. Consider the followings in choose the primary key: The primary key shall be simple and familiar, e.
The value of the primary key should not change. Primary key is used to reference other tables. If you change its value, you have to change all its references; otherwise, the references will be lost. For example, phoneNumber may not be appropriate to be used as primary key for table Customers, because it might change.
Primary key often uses integer or number type. But it could also be other types, such as texts. However, it is best to use numeric column as primary key for efficiency. Primary key could take an arbitrary number. This arbitrary number is fact-less, as it contains no factual information.
Unlike factual information such as phone number, fact-less number is ideal for primary key, as it does not change. Primary key is usually a single column e. But it could also make up of several columns. You should use as few columns as possible. Let's illustrate with an example: Name may not be unique.
Phone number and address may change. Hence, it is better to create a fact-less auto-increment number, say customerID, as the primary key.
Relational Database Design
Create Relationships among Tables A database consisting of independent and unrelated tables serves little purpose you may consider to use a spreadsheet instead. The power of relational database lies in the relationship that can be defined between tables. The most crucial aspect in designing a relational database is to identify the relationships among tables. The types of relationship include: In a "company" database, a manager manages zero or more employees, while an employee is managed by one and only one manager.
In a "product sales" database, a customer may place many orders; while an order is placed by one particular customer.
This kind of relationship is known as one-to-many. One-to-many relationship cannot be represented in a single table. For example, in a "class roster" database, we may begin with a table called Teachers, which stores information about teachers such as name, office, phone and email.
What is a One-to-Many Relationship? - Definition from Techopedia
To store the classes taught by each teacher, we could create columns class1, class2, class3, but faces a problem immediately on how many columns to create. On the other hand, if we begin with a table called Classes, which stores information about a class courseCode, dayOfWeek, timeStart and timeEnd ; we could create additional columns to store information about the one teacher such as name, office, phone and email.
However, since a teacher may teach many classes, its data would be duplicated in many rows in table Classes. To support a one-to-many relationship, we need to design two tables: We can then create the one-to-many relationship by storing the primary key of the table Teacher i. The column teacherID in the child table Classes is known as the foreign key. A foreign key of a child table is a primary key of a parent table, used to reference the parent table. Take note that for every value in the parent table, there could be zero, one, or more rows in the child table.
For every value in the child table, there is one and only one row in the parent table. Children's healthy psychological development is facilitated when the parents are both responsive and moderately demanding.
During toddlerhood, children often begin to assert their need for autonomy by challenging their parents. Sometimes, the child's newfound assertiveness during the so-called terrible twos can put a strain on the parent-child relationship. It is important that parents recognize that this behavior is normal for the toddler, and the healthy development of independence is promoted by a parent-child relationship that provides support for the child's developing sense of autonomy.Entity Relationship Diagram (ERD) Tutorial - Part 1
In many regards, the security of the first attachment between infant and parent provides the child with the emotional base to begin exploring the world outside the parent-child relationship. Preschool Various parenting styles evolve during the preschool years. Preschoolers with authoritative parents are curious about new experiences, focused and skilled at playself-reliant, self-controlled, and cheerful.
School age During the elementary school years, the child becomes increasingly interested in peers, but this is not be a sign of disinterest in the parent-child relationship. Rather, with the natural broadening of psychosocial and cognitive abilities, the child's social world expands to include more people and settings beyond the home environment. The parent-child relationship remains the most important influence on the child's development.
A Quick-Start Tutorial on Relational Database Design
Children whose parents are both responsive and demanding continue to thrive psychologically and socially during the middle childhood years. During the school years, the parent-child relationship continues to be influenced by the child and the parents.
In most families, patterns of interaction between parent and child are well established in the elementary school years. Adolescence As the child enters adolescencebiological, cognitive, and emotional changes transform the parent-child relationship. The child's urges for independence may challenge parents' authority. Many parents find early adolescence a difficult period.
Adolescents fare best and their parents are happiest when parents can be both encouraging and accepting of the child's needs for more psychological independence.
Although the value of peer relations grows during adolescence, the parent-child relationship remains crucial for the child's psychological development. Authoritative parenting that combines warmth and firmness has the most positive impact on the youngster's development. Adolescents who have been reared authoritatively continue to show more success in school, better psychological development, and fewer behavior problems. Adolescence may be a time of heightened bickering and diminished closeness in the parent-child relationship, but most disagreements between parents and young teenagers are over less important matters, and most teenagers and parents agree on the essentials.
By late adolescence most children report feeling as close to their parents as they did during elementary school. Parenting styles Parenting has four main styles: Although no parent is consistent in all situations, parents do follow some general tendencies in their approach to childrearing, and it is possible to describe a parent-child relationship by the prevailing style of parenting. These descriptions provide guidelines for both professionals and parents interested in understanding how variations in the parent-child relationship affect the child's development.
Parenting style is shaped by the parent's developmental history, education, and personality; the child's behavior; and the immediate and broader context of the parent's life. Also, the parent's behavior is influenced by the parent's work, the parents' marriage, family finances, and other conditions likely to affect the parent's behavior and psychological well-being.
In addition, parents in different cultures, from different social classes, and from different ethnic groups rear their children differently. In any event, children's behavior and psychological development are linked to the parenting style with which they are raised. Authoritarian parents Authoritarian parents are rigid in their rules; they expect absolute obedience from the child without any questioning. They also expect the child to accept the family beliefs and principles without questions.
Authoritarian parents are strict disciplinarians, often relying on physical punishment and the withdrawal of affection to shape their child's behavior. Children raised with this parenting style are often moody, unhappy, fearful, and irritable. They tend to be shy, withdrawn, and lack self-confidence.
If affection is withheld, the child commonly is rebellious and antisocial. Authoritative parents Authoritative parents show respect for the opinions of each of their children by allowing them to be different. Although there are rules in the household, the parents allow discussion if the children do not understand or agree with the rules.
These parents make it clear to the children that although they the parents have final authority, some negotiation and compromise may take place. Authoritative parents are both responsive and demanding; they are firm, but they discipline with love and affection, rather than power, and they are likely to explain rules and expectations to their children instead of simply asserting them.
This style of parenting often results in children who have high self-esteem and are independent, inquisitive, happy, assertive, and interactive. Permissive parents Permissive indulgent parents have little or no control over the behavior of their children.
If any rules exist in the home, they are followed inconsistently. Underlying reasons for rules are given, but the children decide whether they will follow the rule and to what extent. They learn that they can get away with any behavior. Indulgent parents are responsive but not especially demanding.
They have few expectations of their children and impose little or inconsistent discipline. There are empty threats of punishment without setting limits. Role reversal occurs; the children act more like the parents, and the parents behave like the children. Children of permissive parents may be disrespectful, disobedient, aggressive, irresponsible, and defiant.
They are insecure because they lack guidelines to direct their behavior. However, these children are frequently creative and spontaneous. Although low in both social responsibility and independence, they are usually more cheerful than the conflicted and irritable children of authoritarian parents.
Disengaged parents Finally, disengaged detached parents are neither responsive nor demanding. They may be careless or unaware of the child's needs for affection and discipline. Children whose parents are detached have higher numbers of psychological difficulties and behavior problems than other youngsters. Parental concerns Child's development is affected by family conditions such as divorce, remarriage, and parental employment. The parent-child relationship has a more important influence on the child's psychological development than changes in the composition of the household.
Parenting that is responsive and demanding is related to healthier child development regardless of the parent's marital or employment status.
- Parent-child relationships
- Hierarchical database model
If changes in the parent's marital status or work life disrupt the parent-child relationship, short-term effects on the child's behavior may be noticeable. One goal of professionals who work with families under stress is to help them reestablish healthy patterns of parent-child interaction. Discipline is also a concern of parents. Children's behavior offers challenges to even the most experienced and effective parents.
The manner in which parents respond to a child's behavior has an effect on the child's self-esteem and future interactions with others. Children learn to view themselves in the same way the parent views them.
Thus, if the parent views the child as wild, the child begins to view himself that way and soon his actions consistently reinforce his self image. This way, the child does not disappoint the parent. This pattern is a self-fulfilling prophecy. While discipline in necessary to teach a child how to live comfortably in society, it should not be confused with punishment.
Coping —In psychology, a term that refers to a person's patterns of response to stress. Culture —A test in which a sample of body fluid is placed on materials specially formulated to grow microorganisms.