L6+-+Develop+Database+Tables+-Section+3

L6+-+Develop+Database+Tables+-Section+3 - ACCOUNTING...

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Unformatted text preview: ACCOUNTING INFORMATION SYSTEMS DEVELOP DATABASE TABLES WHAT IS MICROSOFT ACCESS? A relational database management system that supports small to medium-sized database applications. What is a Relational Database? collection of tables that are related to one another normally contains tables, queries, forms, and reports For example: One table may represent employees personal information, another may represent employees skills, and another may represent employees work history Example table containing employee data. the primary key columns values by definition are unique for each row this value shows the total number of rows in the table each column holds a different characteristic about the row it describes A Table A TABLE A table: is a two dimensional object having rows and columns, and resembling an excel worksheet Rows (or records) in a table are referred to as tuples Rows can be input in any order and sorted as needed later Each row is unique from all other rows in a table Each column (or field) of a table lists a different characteristic known as an attribute Columns can contain only one type of single valued data Data may be in the form of text, numbers, currency, date/time, etc. Columns may be in any order and can be added, deleted, renamed, or moved as is necessary generally the column with a unique identifier ( primary key ) is listed first only tables hold the datano other of the Access objects including queries, forms, or reportshold data Formal Term Common Term Alternative Common Term relation table file tuple row record attribute column field TABLE DESIGN Many tables can be linked together using primary and foreign keys Primary Keys One or more fields that has a unique identifier for that table If more than one primary key it is called a composite primary key Primary keys can NEVER be null value Foreign Keys Secondary field in one table that is a primary key in another table Allows the designer to set up separate tables to maintain all information and not have to input data many times Sales transactions stored in a database system. SCHEMA OF A RELATION A schema is a representation of a table that lists all its attributes and identifies the primary key and, optionally, foreign keys Schema for the Customer table, tblCustomer, with a reduced number of attributes is: Customer(CustomerID , CompanyName, Contact, Address, City, State) Where customer is the table name where CustomerID is the primary key and other attributes are listed and separated by commas...
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L6+-+Develop+Database+Tables+-Section+3 - ACCOUNTING...

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