Information Technology

Elementary structure of SQL consist of three clause, that is SELECT, FROM, and WHERE. SELECT have correspondence to with operation of projection at algebra relational. SELECT used to present attribute list at result of query. FROM have correspondence to with operation of Cartesian product at algebra relational. FROM used as by list an relationship table to process and in evaluation. WHERE have correspondence to with operation of selection at algebra relational. WHERE consist of predicate covering attribute in relationship which emerge at clause of FROM. Clause of WHERE used to determine criterion or predicate which must in fulfilling an relationship as result of query. This clause have the character of optionally, that is can use clause of WHERE or do not. Otherwise use clause of WHERE, hence query conducted by for all tuples at tables of which is mentioned at clause of FROM. Predicate at clause of WHERE can be combined with other relationship operator, like <, <=, >, >=, <> and logic operator, like AND, OR, NOT. Clause of WHERE can be used to conduct query with predicate which in form of an certain value range, that is by enhancing clause of BETWEEN. For attribute which is have type to of string can be conducted by an seeking with certain pattern, that is by exploiting character ‘%’ or ‘_’ (underscore) and enhance clause of LIKE at clause of WHERE ‘%’ for all substring ‘_’ for all appropriate character on course. Clause FROM used to determine tables to be made as source for the seeking of data In conducting query do not only limited to one tables, but is frequently required for relationship some tables at the same time. To present result of query pursuant to certain attribute sequence, hence can be conducted by enhancing clause ORDER BY, given by default is clause ORDER BY is sequence by menial (ASC), but to change to become sequence by is downhill, can be conducted by enhancing clause of DESC after name of attribute.
Functions of aggregation SQL :
• AVG : to get average value an attribute which is have type numeric.
• MIN : to get smallest value an attribute which is have type numeric.
• MAX : to get biggest value an attribute which is have type numeric.
• SUM : to get total value an attribute which is have type numeric.
• COUNT : to get value to the number of tuples.
Value NULL at one particular query can be treated peculiarly, that is earning is also treated for query to use expression of SQL. Manipulation data operations consist of addition of new tuple, distorting of attribute value, and abolition of tuple at one particular tables.
Command of SQL for the definition of data :
• CREATE : to form data bases, index or table.
• ALTER : to alter structure of table.
• DROP : to vanish data bases, index or table.
For the domain of data type cover as follows :
• Char(n) : type of String with length remain to equal to character n (if filled in character length less than n, hence the rest in content with space).
• Varchar(n) : type of String with flexible length, but maximal counted character n.
• Integer or int : integer type 2 byte.
• Smallint : type Integer 1 byte.
• Real, double, precision : type fraction of point floating decimal.
• Float(n) : type fraction of point floating decimal with digit n precision.
• Date : Type of is date of (composing 4 year digit of month, moon, and date).
• Time : time type (consisted of hour, minute, and second).
If an tables have index compositely (alliance), hence conducted by writing down all attribute at clause PRIMARY KEY.

Type Attribute Of E-R Diagram

• Simple attribute that is attribute which do not be elaborated to become attribute sub, or cannot be elaborated to become other attribute.
• Composite attribute is attribute able to be elaborated to become some attribute sub.
• Monovalent attribute addressed at attribute having at most one value to every data line.
• Valuable attribute many is attribute able to contain more than one value, but having same type.
• Value of Null used by when an entity don't have an value to an attribute. Null also designate that an attribute value there no or unknown.
• Generation attribute is attribute which is its value is obtained from processing or can be degraded by other related tables or attribute.

Kind Of Key

• Super Key : representing an gathering which consist of one or more attribute able to differentiate every data line uniquely in a tables.
• Candidate Key : representing minimum attribute gathering able to differentiate every data line uniquely in a tables.
• Primary Key : representing most unique key, briefer, a more regular made by reference. Primary Key can be selected from one of candidate key.

Step Making E-R Diagram

• Identifying and specifying all gathering of entity to involve.
• Determining attributes of key from each gathering of entity.
• Identifying and specifying all relationship gathering among gathering of entity existing along with foreign key.
• Determining degree of cardinalities to every relationship gathering.
• Equipping gathering of entity relationship gathering and with attribute of descriptive (non key).

Gathering of entity which do not have attribute able to function as primary key. Gathering of entity weak contain entity which is its apparition depend on its existence in a relationship to other entity (strong entity).

Queue

Queue represent one data structure type which is often used for the simulation of situation of real world. Queue is an data aggregate of is which addition of element only can be conducted at one particular back part (referred as with side behind or rear), and abolition (intake of element) to pass other back part (referred as with next side or front). Used term if someone enter in a queue is Enqueue. While term which is often wearied by if someone go out from queue is Dequeue. Heap use principle “enter lastly of first exit” or LIFO (Last In First Out), hence at principal queue the used is“ entering is first of exit first” or FIFO (First In First Out). Equally, sequence element exit will is equal to sequence entry.

Tree

Tree is linear data structure form do not having nature and special marking. This structure is usually used to depicting relation having the character of hierarchical between element existing. Simplest example of which we can see in everyday life, specially in family is family ancestry. Tree like picture under referred as with linear of chart where every element can have more than two branch. Simply tree can be defined as element corps which one of the its element is referred as with root and remains other element (so called node) broken to become a number of becoming gathering which each other do not correlate one another, so-called with sub tree, or is also referred as with branch. If us see in each sub tree, hence this is sub tree also have root and its it him each. Besides level, is also recognized by term degree of degree from an node. Degree of an node expressed as to the number of child or born of node. Leaf also is often referred as with external node external of node. So that other node, except root, also is often referred as with node in is internal of node. High deepness or height (depth) from an tree is maximum level of node in the tree lessened by 1. Ancestor an node is all located node in one band with the node of root until node evaluated. Forest is corps a number of tree which do not each other correlating.

Graph

Graph can be conceived as corps of object activity or, for example, town bus route from one terminal to other terminal, route journey of post package at the time of he accompany letter from one house to other house, and other example of is which can be presented by as a graph. Both example of above representing classic example of with theory graph which more knowledgeable with salesman traveling of problem or problem path shortest, which is on its principle look for short band from all place which must fulfill, so that can economize time, energy, and also expense. Graph in general can be defined as dot corps or nodes of vertices and line or arcs edges. Because line always early with an dot and terminated at other dot, hence line can be written down as couple between two dot.

Data structure at algorithm of programming there is some method, that is : stack, queue, tree, graph. Election used method very hinging with data, good in gathering process and also depository its.

Congeniality Programming

Computer only one of the processing so that can be executed by computer, algorithm have to be written in language notation programming is so that named by program. Become program is written in algorithm implementation or materialization is language certain programming so that can be executed by computer. Program written in one of the language of programming and activity making program referred as by programming. People writing program referred as by programmer. Every step in program referred as by instruction or statement. Become, program lapped over of steps instruction. When an instruction executed, hence operations which chime in with the instruction done by computer.

Mechanism Execution of Algorithm by Processing

Marginally computer of lapped over to the four component especial : input apparatus, output apparatus, unit of processing especial and memory unit of processing especial (Central Processing Unit – CPU) is brain” computer, functioning do operations elementary like comparison operation, operate for calculation, operation reading and operation write. Memory is component which functioning or save. Kept in memory is program (containing operations to be done by CPU) and information or data (something that processed by operations). Input apparatus or output (I / O devices) is appliance including program or data into memory, and used by appliance is computer to communicate result its activity. Apparatus input example of is : keyboard, mouse, disk and scanner. Appliance output example of is : monitor, printer, disk and plotter.

Language of Programming

In this time we earn to communicate with computer by using language which we understand. This matter earn us conduct because all expert have succeeded to make dictionary of is so called with language of programming to translate language which we make to become machine language, this dictionary is referred as with Compiler. Process translating of human being language to machine language referred as with compilers.

Elementary Structure Algorithm

Algorithm contain steps of is solving of an problem. The steps can in the form of action sequence, election action and repetition of action. Third of the step type form construction an algorithm. Become, a algorithm can be woke up from 3 elementary structure, that is :

• Sequence

A sequence consist of one or more instruction. Every instruction done alternately as according to its writing sequence. Instruction sequence determine situation of is end of an algorithm. When its sequence is altered, hence its end result possible also will change.

• Selection

A instruction done by if fulfilled certain condition.

• Repetition

One of the excess of computer is its ability to conduct is same work repeatedly without recognizing fatigue. Repetition structure referred as by under layer (loop), and part of repeated algorithm named by under layer body (loop body).

Variable

Variable represent an name of implying location computer memory able to be used for save of value, where its contents earn changes. Variable can show as abstraction of location. Result of evaluation of variable is value of that variable. Value from an variable can be altered with statement assignment. A statement assignment consist of a variable on the left and an expression side its right.

Constantan

Variable having value which in character cannot be altered, value determined at the time of definition.

Type Data

When an declaration variable, hence its type at the same time determined. Type from an variable express :

• Type value able to be kept in memory location for variable, (limiting values gathering able to have by the variable).
• Type operation able to be conducted to variable pertinent.