S511 Session 6, IU-SLIS 1 DB Implementation: MS Access Tables

S511 Session 6, IU-SLIS 2 Outline Overview of RDB Implementation Access Table ► Data Types ► Field Properties ► Relationships MS Access File for Lecture

S511 Session 6, IU-SLIS 3 RDB Implementation: Overview Tables ► Translation of ER model in RDBMS construct ► For data storage entities, attributes, relationships Forms ► Data input/display user interface e.g. data entry form, search form ► For viewing, editing, entering, dynamic querying Queries ► Relational algebra operations combination of join, select, sort, filter, modify, etc. ► For data retrieval & manipulation Reports ► Data display output e.g. monthly reports (set query results) ► Forms can manipulate data, but reports cannot

S511 Session 6, IU-SLIS 4 RDB Implementation: Table Table is the fundamental element in a relational database. ► Contains data about a particular subject row = record = an entity (e.g., an employee, a product) column = field = an attribute (e.g., last name, product description) ► Users seldom see tables if at all. ► Data entry is usually done via forms. Main issues in table design ► What are the key attributes? i.e., primary & foreign keys ► What is the data type for each attribute? e.g. text, number, date, etc. ► What are the properties for each attribute? e.g. size, input/output format, range, etc.

S511 Session 6, IU-SLIS 5 MS Access Table: Data Types Text alphanumeric data up to 255 characters. Memo alphanumeric data with more than 255 characters used for notes or comments can’t search or index on memo data type fields Number numeric data for fields that need to have computational operations done Field Size = 1, 2, 4, 8, or 16 bytes Date/Time dates and times as 8-byte double-precision integers Currency monetary data as 8-byte numbers with precision to four decimal places also used when you don't want to round values. AutoNumber unique values created by Access for each new record cannot be changed once created Yes/No Boolean (true/false, Yes/No, On/Off) good for checkbox type field Hyperlink links that opens a file or a Web address (e.g. URL, address) OLE Object images, documents, graphs, and other objects from Office & Windows-based programs display bitmap image of objects less efficient & flexible than Attachment Attachment any supported files (image, spreadsheet, document, chart, etc.) can edit as well as view files Lookup Wizard tool to create lookup fields in design view lookup field = a list of values derived from existing table fields or a list (i.e. a set of values) MS Access 2007: Data Types & Field Properties

S511 Session 6, IU-SLIS 6 MS Access Table: Field Properties ► Field Size to set the maximum size for Text, Number, or AutoNumber data type. affects the stored value (via rounding, truncation) ► Format to customize the display/print layout of data does not affect the stored value (e.g. Currency  $1,234.50) ► Input Mask to set the data input template to guide data entry e.g. Short Date  MM/DD/YYYY  99/99/0000;0;_ ► Validation Rule to validate/restrict data entry use with Validation Text to display message on validation failure an expression that specify valid data values MS Access 2007: Field Properties Quick Reference

S511 Session 6, IU-SLIS 7 Field Property: Field Size Text data type ► 1 to 255 Number data type number propertiesnumber properties ► determines the precision of the number that can be stored precision = number of significant digits ► AutoNumber is 4 byte ► use Long Integer for foreign keys that refer to AutoNumber primary keys For best performance, use smallest sufficient field size SettingStorage Value (Min, Max)Significant Digits Storage Size Byte(0, 255)N/A1 byte Integer(-32,768, 32,767)N/A2 bytes Long Integer(–2,147,483,648, –2,147,483,647)N/A4 bytes Decimal(-1*10 28, 1*10 28 )2812 bytes Single(–3.4*10 38, +3.4*10 38 ) 74 bytes Double(–1.797*10 308, 1.797* ) 158 bytes

S511 Session 6, IU-SLIS 8 Field Property: Text Format Determines how to display the contents of data in tables ► does not affect the stored value For enhancing readability ► e.g., credit card/phone number ►  Syntax ► format for non-empty text; format for empty text ►  display data as is, or ‘None’ when empty Required character (including space) abc  ( abc) &Optional character(&&&&&): abc  (abc) <Force all characters to ABC  (abc) >Force all characters to abc  (ABC) [color]Display the field’s content in the named abc  (ABC) “text”Display the text btw. quotes.&“ kg”: 16  16 kg \Display next character as entered (same as “”).&\M: abc  abcM *Fill all blank spaces with the next character.&*?: five  five???? (display length=8) !Fill from left instead of right.!*?: five  ????five (display length=8) MS Access 2007: Custom Format for Text & Memo data types

S511 Session 6, IU-SLIS 9 Field Property: Number Format Pre-defined formats ► Currency e.g. displays ‘ ’ as ‘$1,234.56’ ► Percent e.g. displays ‘ ’ as ‘ %’ (requires size = “double”) ► Scientific e.g. displays ‘ ’ as ‘1.23E+3’ Examples ► 0;(0);;”Null” display positive numbers normally, negative numbers in parenthesis, “Null” if the value is null SectionDescription FirstFormat for positive numbers SecondFormat for negative numbers ThirdFormat for zero values FourthFormat for Null values SymbolDescriptionExample 0Display a digit or 0.00,000: 1234  01,234 #Display a digit or nothing.##,###: 1234  1,234 %Multiply by 100 and append % sign##.#%:  12.3% MS Access 2007: Custom Format for Number data types

S511 Session 6, IU-SLIS 10 Field Property : Date/Time Format SymbolDescription dDay of the month in one or two digits (1 to 31) ddDay of the month in two digits (01 to 31) dddFirst three letters of the weekday (Sun to Sat) ddddFullname of the weekday (Sunday to Saturday) m, mm, mmm, mmmmMonth equivalent to d, dd, ddd, dddd yNumber of the day in a year (1 to 366) yyLast two digits of the year (01 to 99) yyyyFull year (0100 to 9999) wDay of the week (1 to 7) h/hh, n/nn, s/ssHours, Minutes, Seconds (1 digit/2 digit) Pre-defined formatDescription Short/Medium/Long Datee.g. 2/28/2003, 28-Feb-03, Friday, February 28, 2003 Short/Medium/Long Timee.g. 13:00, 1:00 PM, 1:00:00 PM General DateCombination of Short date and Long Time as needed e.g. 2/28/2003 1:00:00 PM Example: ddd", "mmm d", "yyyy  Fri, Feb 28, 2003 MS Access 2007: Custom Format for Date/Time data types

S511 Session 6, IU-SLIS 11 Field Property: Input Mask Data input template ► a set of literal and mask characters that control what can and cannot be entered in a field to prevent invalid data entry ► e.g. (999) ;;_ data entry: (___) ___-____  (812) data storage: area code is optional ► e.g. >L<?????????????? Input Mask Character Reference Input Mask Character Reference A first or last name with the first letter automatically capitalized SectionDescription FirstSpecifies the input mask SecondSpecifies whether the data is stored with the literal display characters. - 0 to include literal characters, 1 or blank to store typed characters only ThirdSpecifies the display character for data input positions SymbolDescriptionSymbolDescription 0Required digit (0 to 9)9Optional digit or space (0 to 9) LRequired letter?Optional letter ARequired letter or digitaOptional letter or digit &Required character or spaceCOptional character or space #Required digit, space, or +/-PasswordDisplay entry with * MS Access 2007: Input Mask

S511 Session 6, IU-SLIS 12 Field Property : Format vs. Input Mask Input Mask property ► to control how data is entered ► affects how data is displayed during data entry ► can affect how data is stored Format property ► to display data in a consistent format ► affects how data is displayed after it is saved ► does not affect how it is stored Decimal Places property (for Number data type) ► specifies the number of decimal places to display ► does not affect how it is stored ► must use Field Size property to change how a number is stored ► has no effect if Format property is blank or set to “General Number”

S511 Session 6, IU-SLIS 13 Field Property: Validation Rule ► Validates & Restricts data entry Validation Text holds the error message to be displayed use “expression” to define validation rules  expression is a combination of operators, fields, functions, etc.  expression can be constructed using the Expression Builder ► Other Data validation in MS Access Data Type – e.g., Date/Time Field Size – e.g., 20 char for last name Required – e.g., Yes to require data entry Input Masks – e.g., for zipcode ► Examples Validation RuleDescription <> 0Entry must be non-zero >1000 Or Is NullEntry must be greater than 1000 or blank Like “A????”Entry must be 5 characters and begin with the letter “A” >= #1/1/96# And <#1/1/97#Entry must be a date in 1996 MS Access 2007: Validation Rule

S511 Session 6, IU-SLIS 14 Access Table: Misc. Field Properties ► Indexed create internal record of the field values for searching Access updates all of its indexes every time a table record is added or updated  too many indexed fields can slow down data entry Primary key field should be set to “Yes (No Duplicates)”  exception: set composite primary key fields to “Yes (Duplicates OK)” ► Required Yes/No to indicate whether the data entry is mandatory ► Allow Zero Length Yes/No to indicate whether a zero-length string (“”) is a valid entry (default=yes) ► Caption label for the field (default= field name) ► Default Value value automatically entered for new records ► Unicode Compression compresses unicode character representation  2 bytes to 1 byte when the first byte is 0 (e.g. English) ► IME Mode set Input Method Editor Mode (e.g. Hangul) MS Access 2007: Field Properties Quick Reference

S511 Session 6, IU-SLIS 15 MS Access: Null vs. Zero-length string ► Null A variable state indicating missing data Information that may exist but is unknown  i.e., “I don’t know what the value is.”  e.g., CUS_FAXNUM is set to Null initially. Created by pressing ENTER key in a field ► Zero-length string To handle unknown/non-existent values in required fields Information that does not exist  i.e., “I know there is no value.”  e.g., CUS_FAXNUM is set to zero-length string after discovering that the customer has no fax. Created by entering two double quotes (“”) in a field

S511 Session 6, IU-SLIS 16 MS Access: Lookup Field ► Lookup Field/Column Displays a list of choices in a combo box or list box. The list is retrieved from another table/query or a value list. ► Creating a Lookup field via Lookup Wizard 1.Select Lookup Wizard in Data Type column.  The Lookup Wizard starts 2.Select the data source in Lookup Wizard  Look up the values in a table or a query, or  Type in the values. 3.For Table/Query-based lookup field, a. Choose a table/query b. Select fields (visible + data store) For Value list-based lookup field, a. Enter the number of columns to include in the lookup field. b. Type the values in the grid 4.Choose the filed whose value will be used MS Access 2007: Lookup Field

S511 Session 6, IU-SLIS 17 MS Access: Referential Integrity Necessary Conditions ► Matching field from “one” side of related tables must be a primary key or have the Indexed property set to “Yes (No Duplicates)”. ► Related fields must have the same data type. exception: AutoNumber to Number when both have the same Field Size Effects ► Cannot enter a value in the foreign key field that does not exist in the primary key of the primary table ► Cannot delete a record in the primary table if matching records exists in the related table ► Cannot change a primary key value in the primary table if that record has related records. Cascading Updates/Deletes ► Allows automatic updates/deletes of all related records along with primary record e.g. change in primary key value in the primary table will be reflected in foreign key value of the related table ► Enabled/disabled in the relationships window

1. Create a table. ► Table Design in Create tab 2. Add fields to the table ► Data Type ► Field Properties 3. Set the primary key 4. Save & name the table 5. Set the relationships S511 Session 6, IU-SLIS 18 Table How-To: Overview

Create a table in a new database 1. Click the Microsoft Office Button, and then click New. 2. In the File Name box, type a file name for the new database. 3. To browse to a different location to save the database, click the folder icon. 4. Click Create. The new database opens, and a new table named Table1 is created and opens in Datasheet view. Create a table in an existing database 1. Click the Microsoft Office Button, and then click Open. 2. In the Open dialog box, select the database that you want to open, and then click Open 3. On the Create tab, in the Tables group, click Table Design A new table is inserted in the database and the table opens in Design view S511 Session 6, IU-SLIS 19 Table How-To: Creation

Add a field to an existing table 1. Open a table in Design View. 2. Type a name for the field in the Field Name column. 3. Select an appropriate data type in the adjacent Data Type column.Data Type Text, Memo, Number, Date/Time, Yes/No, etc. 4. Set Field Properties.Field Properties Field Size, Format, Input Mask, Validation Rule, etc. Lookup Wizard S511 Session 6, IU-SLIS 20 Table How-To: Fields

Set a table's primary key 1. Select the table whose primary key you want to set or change. 2. On the Home tab, in the Views group, click View, and then click Design View. 3. In the table design grid, select the field or fields that you want to use as the primary key. To select one field, click the row selector for the field that you want To select more than one field, hold down CTRL, and then click the row selector for each field 4. On the Design tab, in the Tools group, click Primary Key. A key indicator appears to the left of the field or fields that you specify as the primary key ► To add an Autonumber primary key In the Field Name column of an empty row, type a name (e.g., CustomerID) In the Data Type column, click the drop-down arrow and click AutoNumber. S511 Session 6, IU-SLIS 21 Table How-To: Primary Key

Create table relationships 1. Open a MS Access database. 2. On the Database Tools tab, in the Show/Hide group, click Relationships. 3. On the Design tab, in the Relationships group, click Show Table. If you have not yet defined any relationships, the Show Table dialog box automatically appears. 4. Select tables and then click Add. When finished, click Close. Click Tables in the Show Table dialog box to see only tables. 5. Drag the primary key from one table to the foreign key in the other table. To drag multiple fields, press the CTRL key, click each field, and then drag them. 6. Verify that the field names shown in the Edit Relationships dialog box are correct. If a field name is incorrect, click the field name and select a new field from the list. Select the Enforce Referential Integrity check box. 7. Click Create. S511 Session 6, IU-SLIS 22 Table How-To: Relationships