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CIS-145Test 1 Review

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DatabaseCollection of related data and tools to use,

manage dataRelational database

Data stored in tablesEach table stores data about one thingCommon values create connections

(relationships) between tables

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Fields, Records, and TablesFields

Basic unit of data represented by a column in a table datasheet

RecordsGroup of related fields or all fields related to a

specific item: person, place, or thing Each row of a datasheet represent a record

TablesGroup of related records

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Planning a DatabaseWhat information do you want to obtain? What data elements (fields) must you include to be

able to get the information?What types of data will you enter into each field?

Dates, numeric values, amounts of money, text, etc.What fields of data relate to the same basic items and

belong grouped together? How do the groups of data relate to each other? What questions will you need the database to be able

to answer? What is the most efficient way to get data into the

database tables?

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Creating Tables Each table should contain fields that focus on

data specific to one type of itemSuch as customers, employees, inventory, etc.

Each table should have a primary key Fields in the primary key cannot be empty

(null)May be one or more fields

Each generic field# heading is replaced with a descriptive field name

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Table Design GuidelinesStore all necessary dataStore data in smallest partsAvoid calculations

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Using Table Design ViewPresents a blank work area on which to

enter fieldsProvides tools for setting data types,

descriptions, and propertiesEnables you to change the structure

and organization of fields in the table

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Entering Field NamesField names:

Short but descriptiveCan contain alpha-numeric charactersCan contain many symbolsCan contain spacesMust start with a character or symbol

May use naming conventionIdentify table, data type, and field description

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Identifying Data TypesData types identify the kind of data to be

added to a fieldTextNumbersDates/TimesCurrency

Setting a data type controls values that the field contains

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AutoNumber FieldsFields that automatically number records as

you add them to a tableNumbers can’t be entered or changed by

userIf you delete a record from a table, or cancel

a new row, Access never assigns the number to any new record

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Field PropertiesField Size determines how much data can be

storedSome data type sizes are fixed – date/time,

yes/noFormat controls how a value is displayedInput Mask controls which keyboard entries

will be required and acceptedValidation Rule sets limits on values that a

field will acceptValidation Rule applies regardless of how data

is entered or changedSet Validation Text to explain how to correct an

entry

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OperatorsOperators are used in validation, calculations

and queriesComparison Operators:

Relational Operators (=, >, <, <>, >=, <=)Patterns (Like)Compare to a list (In)

Logical operators define how to tie tests togetherAnd, Or, Not

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Using WildcardsUsed in patterns instead of specific

charactersPrimary wildcards used:

* Represents any number of characters? Represents an individual character

Examples:*Graham* locates all records with graham within

the textGra?am locates all records with gra at the

beginning of the field value and am at the end of the field value with only one letter between

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Relational DatabasesHave more than one table where tables are

related to each otherOne to oneOne to manyMany to many

A combination of fields may be used for the table’s primary key

One to Many RelationshipsEach table contains data about a specific

subject (customers, loans)Each table on the ‘one’ side has a primary

keyPrimary key of the “one” table is a foreign

key in the many table

Many to Many RelationshipsTwo tables are related, but can have many

records in each table in commonOne student can attend many courses; one

course can be attended by many studentsImplement a many to many relationship by

creating a pair of one to many relationships with a third tableThird table is often referred to as a “join” or

“junction” tableEntries in the join table point to rows in the

original tables

Foreign KeyA foreign key points to a record in another

tableForeign key “looks like” the related primary

keySame number of fieldsData types for each field must matchField names don’t matter

Referential IntegrityMakes sure that the records in related tables

are consistentMust have a customer in the customer table for

an order assigned to that customerAvoids “orphans”

Cannot delete a record or change the primary key in the one table when associated records are in the many table, unless have cascade delete and cascade update enabled

Editing DataMaking new entries, changing existing

entries, and deleting rows are all affected by referential integrityA customer can be added at any timeMust have a customer before a loan can be

entered and associated with a customer Referential integrity doesn’t require entry into a

foreign keyCan delete a loan at any time, but can only

delete a customer if they don’t have any loans (assuming no cascade delete)

Cascading ChangesWhen referential integrity is enforced can

choose to include Cascade Update and/or Cascade DeleteCascade update passes changes to the primary

key of the “one” table to the related rows in the “many” table

Cascade delete removes rows from the “many” table when a primary key (row) is deleted from the “one” table

Relationships WindowWhere relationships between tables are

created and definedRelated fields must have the same data type

Autonumber is related to number field with long integer field size

The one table has a 1 next to it; the many has

a next to it

Autolookup QueriesUse queries to automatically look up data

from related tablesMust contain the foreign key from the many

tableCan add, change or delete data in the source

tables