DataBase Creating

- create an empty db- add a table- define columns (name and data type)- input data to the table

- define forms, queries

Designing - processing

• the DB is a collection of tables, queries, forms and other• Every elements of a DB has his own „project”. The table

has the project of columns and data type. The query has columns and conditions. The form has fields.

• Every element of a DB participates in data processing. Tables collect data elements as numbers, string, OLE.

• Another elements collect the processed data.• When DB elements are designed the DB can not be

processed ! The processing require to complete the design

Process of DB creating

Define a source table- columns,- data type (numbers, string, date, logical)

Query on the table

[parameters]

conditions

The query produces a virtual table

Forms are defined on tables

The designer

the OLE data type in the table

The table

COL1 COL2 IMG1

Flower Rose Link to the image „rose”

Tree Oak Link to the image „oak”

COL1 COL2 IMG1

The form

The navigation bar

Flower Rose

The bmp or jpg or other file

Processing the data

• create DB of tables, queries and forms• input data to tables• call the forms or queries• test if the output data fulfill yours requirements• add a new feature to the DB design

The table

• the table is a collection of rows,

• the row consist of fields, which reflects the properties of some real entity,

• the field can be a number, text or link,

• the field has a format, used for input – output a data in field,

• the rows has the same fields, collected in columns of a table

The table reflects real objects (an example)

Objects

Object Propulsion Weight

boat winter small

car engine middle

shuttle rocket huge

Data type

• An real object has properties (attributes)– examples: name, quantity, size, weight, colors, shape,

temperature, the date of validity– the attributes are expressed by words (a letters string)

or numbers, which have formats– examples of a name: alfa, beta, gamma, A1, B1, G1– examples of a number: 10, 20 (the integer format),

10.01, 20.001 (the float format), 10-12-05, 10-dec-05 (the date format)

• A set of properties (attributes) of the real object defines the „entity”, which is mapped to a row of a table

• Real objects may depend one of another.• Usually a set of objects related to one object but there

are two o more types of objects.• Each type of object is mapped by a table.• Example: a student can borrow books from the library,

this means an object student has a related set of books.

• Students and books are mapped to tables

Related tables

booksA student

has borrowed

Example of the related tables – part 1

• A simply way is to map students to a table and books to a table as follows.

Name School Address

Pirx Astro Luna

Alex Astro Mars

Students

Title Author Borrowed

Limes inferior Janusz Zajdel Yes

Dzienniki gwiazdowe Stanisław Lem Yes

Books

• The example shows two independent tables.

Example of the related tables – part 2

• The relation of a student and books has to be mapped by the structure of the tables.

• In the example the table of books has an additional column, which include the data from one column of the students table

Name Title Author Borrowed

Pirx Limes inferior Janusz Zajdel Yes

Alex Dzienniki gwiazdowe

Stanisław Lem Yes

Books

The column from the students table

Searching for the data in a table

• the data in a row maps properties of a real object,• a table consists of rows, which maps the real objects,• the table can include a huge amount of rows,• in order to find a row, which reflects the specific property

of an object it is defined a key,• the key can be one column or more columns,• setting a value of the key and using the searching engine

the rows is retrieved from a table,• a key and the searching engine is the query on a table,

Query on a table

data1

data2

data1

[KEY] = data2

Query data2

Source table

Virtual table – an output of the query

The key value in a query

• A simple query is a key over one column of a table• A key has to be defined by value• A key is a type of the data in one column of a table• The data can be a type: „numbers”, „string”, „date”, OLE• Examples of a data: 3.1473520, „asd0fgh”, 01-may-05• A simple query has two forms:

– „equal to” defined by the sign =– „garter then” also „less then” defined by signs < >

• The simple query can be used over one or more column, in order to select the data which fulfill the conditions of all keys

Query on a table using keys

c11 c12 c13

c21 c22 c23

c31 c32 c33

c41 c42 c43

[KEY1] = c31, ….. , [KEY2] = c33

Query

Source table

c31 c32 c33

Query using logical expression

• Defining a query with a few keys a row is retrieved when the data in the row fulfill the condition: „first key is true” and „second key is true” and all next keys is true.

• This condition is a logical expression in the form as:

[key1] and [key2] and „all next keys”• The expression is used to retrieve data from a table

assuming the data fulfill the condition:„Data from column 1” = [key1] and „Data from column 2” and [key2] and next …

• The brackets allow to clarify the expression:(„Data from column 1” = [key1]) and („Data from column 2” and [key2]) and

next

Logical expression – an example

code a sign

50 A

51 B

52 C

53 D

54 E

(50 < [code]) and ([code] > 53)

code a sign

51 B

52 C

Query on related tables

• Query on related tables joins the data from the tables.• Query includes one or more columns from tables• The example joins the all data from the students table and

the books table

Name Title Author Borrowed

Pirx Limes inferior

Janusz Zajdel

Yes

Alex Dzienniki gwiazdowe

Stanisław Lem

Yes

Name School Address

Pirx Astro Luna

Alex Astro Mars

Name School Address Title Author Borrowed

Pirx Astro Luna Limes inferior Janusz Zajdel Yes

Alex Astro Mars Dzienniki gwiazdowe Stanisław Lem Yes

Query

Input and output data from a table using the form

• Tables, collected in database, store data• The data can be input and output from a table using a

form as interface• The input and output of data processes only one row of a

table• Forms are two types:

– „the columns form” when only one row in a form,– „the browser form” when a few rows in a form

• The form can process data from a few tables

The form for related tables

• Two tables are related when the data from tables can be joined by a query or a form

• A form over related tables (usually) is the columns form which include the browser form

• A columns form processes one row from the main table• A browser form processes rows from the subordinate

table• The columns form includes the browser form• A row is processed by the main form and the browser

processes rows which are related to the main

The form for related tables – an example

The columns form

A row from the main table

The browser form

Rows from the subordinate table

Related tables