Database%20Management:%20Tables

1
Database Management Tables

• INFO and TABLES module
• Getting Attribute Data into Arc/INFO
• Modifying Feature Attribute Tables in Tables or
  INFO
• Inputting from and Outputting to External Files
• Modifying Feature Attribute Tables in Arc and
  ArcPlot
• Join and Relate tabular data

2
Intro to Tabular Database Management

• The information which describes and quantifies
  spatial features in the ARC/INFO GIS is stored in
  INFO files and, optionally, in external database
  management system (DBMS) tables.
• INFO is a totally stand alone relational database
  management system exclusively dedicated to
  Arc/INFO.
• Each ARC/INFO module (Arc, ArcEdit, ArcPlot,
  Tables, INFO) provides some tools for managing
  and changing these tables
• There are two types of attribute tables feature
  attribute tables and related tables.
• Feature attribute tables are generated by the
  ARC/INFO software when you create a feature class
  topology, and must be in INFO file format
  (discussed in depth in first lecture)
• Related attribute tables can be either INFO files
  or external DBMS tables.

3
Review Feature Attribute Tables

• Types of feature attribute tables
• Points - Point attribute table - PAT
• Arcs - Arc attribute table - AAT
• Polygons - Polygon attribute table - PAT
• Each contain both internally generated
  topological data plus user defined attributes --
  See Introductory lecture for data stored in each
• To look at data variables (items) in a feature
  attribute table
• Arc items ltcovergt.pat or Arc items
  ltcovergt.aat
• Arcplot items ltcovergt ltfeature_classgt
• Info or Tables items (after having selected the
  feature attrib table)
• To look at data stored in each item
• Arc list ltcovergt.pat or Arc list
  ltcovergt.aat
• Arcplot list ltcovergt ltfeature_classgt
• Info or Tables list (after having selected the
  feature attrib table)
• Be sure to note difference in usage for ITEMS and
  LIST between Arc and ArcPlot!!!!

4
Sample Item Definitions

• Example
• Arc items pub.pat
• COLUMN ITEM NAME WIDTH OUTPUT TYPE
  N.DEC
• 1 AREA 4
  12 F 3
• 5 PERIMETER 4
  12 F 3
• 9 PUB
  4 5 B -
• 13 PUB-ID 4
  5 B -
• 17 ID
  8 12 F 0
• 25 NAME 25
  25 C -
• 50 ADDRESS 15
  15 C -
• 65 CITY
  12 12 C -
• There are 8 items (variables). The first 4 are
  standard, crated by Info. The last 4 are user
  created.

5
Understanding Item Definitions

• An item (column) is described in terms of four
  variables
• name - the name of the item, up to 16 characters
  in length
• e.g. cover-id, landuse, pop97, etc.
• type - the data types used to store values
• I - integer (one byte per digit)
• B - binary integer (requires less storage than I
  types)
• C - character
• N - floating point (e.g. decimal) number stored
  as one byte per digit
• F - floating point binary number
• D - date (e.g. yyyymmdd)
• width - the width of the item in bytes required
  for storage
• I - 1-16 bytes B - either 2 or 4 bytes
• C - 1 to 320 characters N - 1 to 16 digits
• F - 4 for single, 8 for double precision D -
  always 8 bytes
• For F or N also provide the number of decimal
  places for real numbers
• Output width - the width of item values when
  displayed

6
How do you know which item types to specify?

• If the attribute values contain any non-numeric
  characters, you must specify type C.
• If the values are numeric with a decimal place,
  you must use N or F. Storing numeric values as F
  (floating point binary) allows you to store large
  numbers in a small amount of space (4 bytes).
• If the values are numeric with no decimal, store
  them as I or B. Again, using B (binary) saves
  storage space.
• You can store numeric values as characters but
  you cant manipulate characters arithmetically.
• How do you know how much space to specify?
• Define the item width for types C, I or N to
  accommodate the longest value to be stored
  unnecessarily long widths waste storage space.
• Output width should be sufficient to display the
  longest character string or numeric value.
  Always include one space for the decimal and one
  for negative sign.

7
List

• 3
• AREA 11278215.000
• PERIMETER 17881.912
• LULCSP 3
• LULCSP-ID 41
• LULC_CODE 41
• Continue?
• LEVEL_I FOREST LAND
• LEVEL_II DECIDUOUS FOREST
• 4
• AREA 2316684.250
• PERIMETER 6632.658
• LULCSP 4
• LULCSP-ID 11
• LULC_CODE 11
• LEVEL_I URBAN OR BUILT-UP
• LEVEL_II RESIDENTIAL
• 5

• To look at data stored
• Arc list lulcsp.pat
• 1
• AREA
• PERIMETER 26829452.50
• LULCSP 1
• LULCSP-ID 0
• LULC_CODE 0
• LEVEL_I
• LEVEL_II
• 2
• AREA 12154654112
• PERIMETER 3137822.500
• LULCSP 2
• LULCSP-ID 21
• LULC_CODE 21
• LEVEL_I AGRICULTURAL LAND

8
Reminder File Structure

• The INFO directory for a coverage is at the same
  directory level as the coverage.
• All coverages have several INFO files, the most
  common of which are the feature attribute tables
  (.pat or .aat).
• The coverage to which info files correspond is
  not apparent, therefore
• Always use Arc copy to copy coverages to another
  directory. Never use your operating system to
  copy coverages
• Always use Arc copyinfo to copy INFO files which
  are not associated with a coverage. Again, these
  files are not identifiable with your operating
  system. To find their names use Arc dir info,
  or use dir in Tables or INFO
• However, you may also use or generate text files
  outside of the INFO database. You will only be
  able to see these (and copy or delete them) using
  your operating system (e.g. with Windows
  Explorer)

9
Sample Data Management Commands

• COMMAND MODULES (usage will differ)
• ITEMS Arc, ArcPlot, ArcEdit, Tables, INFO
• LIST Arc, ArcPlot, ArcEdit, Tables, INFO
• RESELECT Arc, ArcPlot, ArcEdit, Tables, INFO
• ADDITEM Arc, ArcEdit, Tables
• DROPITEM Arc, ArcEdit, Tables
• JOINITEM Arc, ArcEdit, Tables
• CALCULATE ArcPlot, ArcEdit, Tables, INFO
• MOVEITEM ArcPlot, ArcEdit (use MOVE in tables,
  info)
• RELATE (series) Arc, ArcPlot, ArcEdit, Tables
• SELECT ArcEdit, Tables, INFO
• DIR Tables, INFO
• DEFINE, ERASE Tables, INFO
• MOVE Tables, INFO (use moveitem in arcplot,
  arcedit)
• ADD, ADD FROM Tables, INFO
• UPDATE Tables, INFO
• ALTER, MODIFY Tables, INFO
• REDEFINE Tables, INFO
• KILL Tables, INFO

Always remember, check usage since it can differ
between modules!
10
INFO and TABLES

• INFO and TABLES are two programs supplied with
  Arc/INFO for managing attributes.
• INFO is the main relational database management
  system for Arc/INFO.
• TABLES also provides table management with a
  subset of INFO functions. TABLES provides all
  the functionality needed for most database
  management tasks, and is a little easier to get
  into and out of and is less case sensitive than
  INFO.
• INFO is case sensitive and requires all
  parameters, data set names and variable (item)
  names to be typed in UPPERCASE
• Also, you are first prompted for username
  specify ARC
• No usage help available at the INFO prompt. Can
  enter help and the command name, and get
  none-GUI help, or access ArcDoc from NT Programs
  menu.
• Both TABLES and INFO access the same data files.
• Cannot use amls or watch files in Tables or INFO
• Conclusion generally use TABLES
• Do not forget, some table management and change
  is also done from Arc and ArcEdit

11
Comparison of Tables to Info

• TABLES
• Create New Files
• Add data
• Display data
• Extract data
• Manipulate data
• Stack relate files (ARC relate)
• Create items
• Redefine items
• Limited changes to item definitions
• Undo changes
• Use with AML transparently

• INFO
• Create New Files
• Add data
• Display data
• Extract data
• Manipulate data
• Stack relate files (INFO relate)
• Create items
• Redefine items
• Limited changes to item definitions
• Use with AML through data block
• Write reports
• Program
• Input forms for data entry

12
Listing INFO File names

• Files in INFO cannot be seen by name in your NT
  Explorer Window -- they reside within the INFO
  folder with an internally generated name (e.g.
  arc0003.dat and arc0003.nit).
• You can list all INFO file names by using the DIR
  INFO command in Arc,
• Arc dir info
• in INFO or in TABLES this is abbreviated to just
  DIR.
• Tables dir
• Be clear on the difference between dir info and
  lc (listcoverages)
• lc simple names the coverages in your workspace
• Dir info names all the INFO files in your work
  space including those associated with a coverage
• There are normally at least 3 INFO files
  associated with each coverage.pat and/or .aat,
  .bnd, .tic

13
Internal and External INFO Tables

• INFO files can be internal or external. The
  terms refer to where the data are physically
  stored on your computer system.
• INTERNAL FILES
• Data located in a data file internal to the INFO
  directory
• arcxxxx.dat contains the actual data
• Examples of Internal files
• lookup tables
• data files from somewhere else, not topologically
  linked to a coverage, but they have been
  converted from original format into INFO file
  format
• EXTERNAL FILES
• Data located in a data file external to the INFO
  directory
• arcxxxx.dat contains a pointer to the actual data
  in the form of a pathname
• Examples of External files
• feature attribute tables (.pat, .aat, .nat)
• coordinate tables (.tic, bnd)
• Both types are accessed the same way from within
  INFO or TABLES

14
SELECT and RESELECT

• In Tables and INFO, these commands generally must
  be issued before you can work on tables.
• SELECT selects a file (table), and by
  implication all records within it. Any commands
  subsequently executed will affect all the records
  in the table. You must select a table in Info or
  Tables before you can work on it. To modify only
  specific records, use RESELECT to create a
  subset of records after you have issued SELECT to
  identify the table.
• SELECT ltinfo_file_namegt
• To clear selected table, issue SELECT without a
  name (you seldom do this, since normally you
  simply select another table.)
• RESELECT (reduce select, or record select)
  selects a subset of records from the currently
  selected data file. (In INFO and Tables, you must
  have issued SELECT first to select this data
  file.) Selection criteria are based on logical
  expressions
• RESELECT BY FOR ltlogical_expressiongt
• RESELECT FOR ED-YRS LE 4 OR PAY-RATE GT 17.00
• ASELECT adds additional records to the selected
  set -- requires a logical expression to select
  additional records.
• To clear a selection, use ASELECT without a
  logical expression to clear selection in effect,
  this adds back all records in the file, thus
  clearing all previous selections.
• NSELECT switches the set of selected and
  unselected records.

15
Sample TABLES Session

• Arc Tables (starts tables)
• Enter command directory (will list all files,
  internal and external, within INFO)
• Enter command select pub.pat (you must select
  a file before operating on it)
• Enter command items (will display item names
  in currently selected file)
• Enter command list (will display data in
  currently selected file)
• Enter command quit (will quit Tables and return
  to Arc prompt)
• Sample INFO Session
• Arc info
• ENTER USER NAMEgt ARC (must switch to all
  CAPITAL letters)
• ENTER COMMANDgt DIR (abbreviation for
  directory)
• ENTER COMMANDgt SELECT EDGEROAD.AAT (selects
  table)
• ENTER COMMANDgt IT (abbreviation for items)
• ENTER COMMANDgt Q STOP (to leave INFO)

16
Getting Attribute Data into Arc/INFO

• Step 1 DEFINE a new INFO data file templateto
  hold the attributes
• Data file must contain either
• the coordinate data needed to generate a new
  coverage, or
• a variable that can be used to relate or join to
  an existing coverage feature attribute table.
• Step 2 ADD the attribute values to the INFO
  data file, either by
• entering each value at the keyboard, or
• ADD FROM (or GET) an existing text file.
• Alternate Use JOINITEM or RELATE to connect
  an INFO data file to the feature attribute table
  for the coverage

17
Step 1 Getting Attribute Data into Arc/INFO

• DEFINE - Issue the DEFINE command with the file
  name to create a new data file template. You
  will be prompted for the attribute name, size,
  and type of each item in a new data file.
• Arc tables
• enter command define landuse.dat
• item name landuse-id (common name and
  definitions to match
• item width 4 attribute table to which you
  wish to join)
• output width 5
• item type B
• item name lu-code (new variable)
• item width 3
• output width 3
• item type I
• item name ltreturngt (to end)
• If you make a mistake while defining the file,
  the command ERASE will delete the file, and you
  can start over. Or use ALTER or MODIFY.
• Look at what you have created with the ITEMS
  command.

18
Step 2, page 1 Getting Attribute Data into
Arc/INFO
ADD - use to interactively enter attribute data
into an INFO data file

• Arc tables
• Enter command select Landuse.dat (file we
  created with the DEFINE command)
• Enter command add
• 1
• Landuse-idgt 59
• Lu-codegt 400
• 2
• Landuse-idgt 60
• Lu-codegt 200
• 3
• Landuse-idgt 61
• Lu-codegt 400 ...
• 6
• Landuse-idgt ltreturngt

• Sample table (LIST command)
• Landuse-id lu-code
• 59 400
• 60 200
• 61 400
• 62 300
• 63 100

If any item values are wrong, you can use the
UPDATE command to change the value of a
particular record - works on one record at a
time.
19
Step 2, page 2 Getting Attribute Data into
Arc/INFO

• You can use the GET or ADD FROM commands to read
  attribute values directly from an ASCII file or
  INFO file.
• Remember, when you are in INFO, you are in the
  /info folder. If reading an ascii file, you must
  indicate that the file is stored up one directory
  level.
• GET will put the data values from an existing
  file, which can be an ascii file, a binary file,
  or an INFO file, with fixed record length, fixed
  item length, into an empty INFO table that has
  been defined to match the ascii file field
  definitions.
• enter commandgt GET ../airports.txt COPY
  (using INFO)
• tablesgt get airports.txt copy
  (using tables)
• ADD FROM requires an ASCII comma-delimited file,
  which may have been created with a system text
  editor, or by other programs such as spreadsheets
  or statistical systems. The items in the
  delimited data file must match the items
  definitions of the selected file. Character items
  containing blanks must be enclosed with a double
  quote.
• Enter commandgt ADD FROM ../airports.dat
• Tablesgt add from airports.dat

20
Example using ADD FROM

• Remember that you are in INFO and you must
  specify the full pathname to the ascii file, or
  indicate a move up the directory path
• Arc tables
• tablesgt SELECT LANDUSE.DAT (file previously
  created with DEFINE)
• tablesgt ADD FROM C/USR/DLAUDER/DATA/LANDUSE.TAB
• tablesgt LIST
• tablesgt Q
• The records are added to landuse.dat in the same
  order they were listed in the ASCII data file
• Landuse.dat can now be joined/related to a
  feature attribute table.
• In the input file, text items containing blanks
  must be enclosed in double quotes otherwise the
  blanks are also treated as delimiters and data is
  split among multiple items (this is not in
  ArcDOC!)

21
Getting Attribute Data into Arc/INFO from a DBF
format

• Database files (.dbf) can be converted from dbf
  to an INFO file format with a conversion command
  at the Arc prompt
• Arc DBASEINFO ltdbase_filegt ltinfo_filegt
  DEFAULT DEFINE
• Arc dbaseinfo air_data.dbf airdata
• After conversion to INFO format, the INFO file
  can be joined or related to the coverage feature
  attribute table.
• Remember, files in INFO cannot be seen by name in
  your NT Explorer Window -- they reside within the
  INFO folder with an internally generated name
  (e.g. arc0003.dat and arc0003.nit). You can
  confirm their existence by using the DIR INFO
  command in Arc, or just DIR in INFO.

22
Modifying Item(Variable) Definitions in a File

• MODIFY is used to replace (change), insert and
  delete item definitions such as their name type
  or width BEFORE addition of data records to the
  template file. Must have an empty template--item
  definitions have been defined but attribute data
  has not yet been added (or all data records have
  been PURGED).
• R replace
• I insert
• D delete
• L list
• ALTER is used to alter item definitions such as
  their name, type, or width AFTER addition of data
  records to the file. Items must be empty to
  decrease column width or decimal precision.
• REDEFINE allows you to access contiguous items or
  parts of items in an INFO file as if it were
  another item.
• Items are formatted based on the columns (space
  holders) they occupy. This allows the user to
  view and manipulate the data in those columns as
  a new item.

23
Modifying Record (item) Values in a File

• UPDATE allows you to change the values of
  specific records for any item in the currently
  selected file. UPDATE first prompts you for the
  number of the record to update. The current item
  values for that record are then listed, followed
  by an Edit? Prompt. To change a value, type the
  name of the item you want to change followed by
  an and the new value
• Enter record number 2 (will list current
  values for that record)
• edit? soil_type 30 (or soil_type
  clay if defined as character)
• edit? ltreturngt
• Enter Record Number ltreturngt
• CALCULATE assigns new values for a numeric data
  item for the currently selected records
  (Tables N, I, F, B, D INFO I, N, D).
• enter commandgt calculate item_name
  new_value
• enter commandgt calculate item_name_2
  item_name_1 value
• Same functionality as CALCULATE in ArcPlot. Note
  spaces surrounding sign!!
• MOVE assigns new character data item (C) for
  selected records
• enter commandgt move new char string
  to item_name
• enter commandgt move item_name_1 to
  item_name_2
• For the same functionality in ArcPlot use
  MOVEITEM. (MOVE is very different in ArcPLot!)
• PURGE removes all selected records from a table
  (but item definitions remain--handy, for example,
  if ADD FROM screws up, and you need to try
  again). KILL deletes the entire file.

24
OUTPUT

• OUTPUT will output data from an INFO file into an
  ascii file
• Must be done from INFO (not Tables)
• When creating an ascii file, must precede the
  file name with the symbols to move up one
  directory level ( ..\ ) to be out of info
  folder
• If there are more than 999 records, INFO will
  insert a comma in the record number (e.g. 1,000).
  To prevent the commas
• enter commandgt CALC COMMA-SWITCH -1
• Example to create an output file with user-id and
  x,y coordinates that will be used to generate a
  point coverage
• arc INFO
• ENTER USER NAMEgt ARC
• ENTER COMMANDgt SELECT AIRPORTS
• ENTER COMMAND gt CALC COMMA-SWITCH -1
• ENTER COMMAND gt OUTPUT ..\points.gen
• ENTER COMMAND gt PRINT COVER-ID, ,,
  LONG, ,, LAT (adds commas also)
• ENTER COMMAND gt PRINT END
• ENTER COMMAND gt OUTPUT ARC.NSP (directs
  future output back to normal default)
• ENTER COMMANDgt Q STOP

25
Coverage Generation

• You can generate a new coverage from any
  comma-delimited ascii file that contains a unique
  identification number (will become the ltcovergt-id
  variable, or user-id) and coordinate pairs for
  points, lines, or polygons.
• Prior to creating a coverage, determine if you
  would like single precision (coordinate accuracy
  to 3 decimals for geographic decimal degree) or
  double precision (coordinate accuracy to 6
  decimals)
• EXAMPLE FOR POINTS
• Arc precision double
• Arc generate airports
• Generate input airports.gen
• Generate points
• Generate quit
• Arc
• Remember to build topology after creation of a
  new coverage
• Arc build airports point
• Coverages are covered in more detail in the
  Coverage lecture!

26
Managing and Changing Tables in
Arc/ArcEdit/ArcPlot

• Some table change and management can also (or
  must) be done outside of Tables and INFO in Arc,
  ArcEdit or ArcPlot.
• Some of the commands previously discussed for
  Tables and INFO will also work outside Tables and
  INFO (altho exact usage may differ)
• Material which follows provides examples of this

27
Modifying item definitions in Feature Attribute
Tables

• ADDITEM add an item to an existing table
• ADDITEM ltin_info_filegt ltout_info_filegt
  ltitem_namegt ltitem_widthgt ltoutput_widthgt
  ltitem_typegt decimal_places start_item
• Example Arc additem pub.pat pub.pat relat-id
  12 12 N 2 city
• - provides column and title only, no data is
  assigned
• - if the ltout_info_filegt is the same as the
  ltin_info_filegt, the existing ltin_info_filegt
  will be replaced
• DROPITEM drop an item from an existing table
• DROPITEM ltin_info_filegt ltout_info_filegt
  drop_item
• Example dropitem pub.pat pub.pat relat-id (to
  drop item relat_id)
• or
• dropitem pub.pat pub.pat (you will be
  prompted for names of all
  items to be dropped)

28
Modifying numeric records in Feature Attribute
Tables

• CALCULATE assigns numeric values to items.
• CALCULATE ltcovergt ltfeature_classgt
  lttarget_itemgt ltarithmetic_expressiongt
• or
• CALCULATE ltinfo_filegt INFO lttarget_itemgt
  ltarithmetic_expressiongt
• Example Arcplot calculate pub point
  key 1
• Arcplot calculate pub.pat INFO
  key 1
• Example 2 Arc tables
• Enter command select aircover.pat
• Enter command calculate air-id
  aircover-id
• Enter command quit
• Arc list aircover.pat (to make
  sure variables correctly calculated)
• - Requires that item key has been defined as
  numeric
• - The CALCULATE command operates on all
  currently selected features within the coverage,
  or all selected records in the INFO file. This
  may be one, some or all records.
• Note there must be a space on each side of the
  equal sign a b

29
Modifying character records in Feature Attribute
Tables

• MOVEITEM assigns a character value to a character
  item
• MOVEITEM ltcovergt ltfeature_classgt
  ltcharacter_string source_itemgt TO
  lttarget_itemgt
• or
• MOVEITEM ltinfo_filegt INFO ltcharacter_string
  source_itemgt TO lttarget_itemgt
• Example Arcplot moveitem pub point blue to
  key
• Arcplot moveitem pub.pat INFO blue
  to key
• - Requires that item key has been defined as
  character
• - Character strings are always placed in single
  quotes
• - The MOVEITEM command operates on all currently
  selected features within the coverage or records
  from an INFO data file this could be one, some
  or all records in the file
• -use the command MOVE in INFO and Tables for
  same functionality as MOVEITEM in Arc and ArcPlot

30
Merging Tables with JOINITEM

• JOINITEM permanently merges two INFO data files
  based on a shared item
• JOINITEM ltin_info_filegt ltjoin_info_filegt
  ltout_info_filegt ltrelate_itemgt start_item
  LINEAR ORDERED LINK
• - The ltrelate_itemgt must exist for both files.
• - The ltrelate_itemgt must have the same
  definitions (i.e. name, type, width, output) in
  both files.
• -LINEAR ORDERED LINK specifies how
  ltjoin_info_filegt records are matched to
  ltin_info_filegt records.
• LINEAR - both files can be sorted in any order.
  This is the default option.
• ORDERED - the ltjoin_info_filegt must be sorted on
  ltrelate_itemgt.
• LINK - The ltrelate_itemgt value in each record of
  ltin_info_filegt indicates the internal record
  number in ltjoin_info_filegt which is to be merged.
  
• - The speed of execution will depend on the
  organization of the files being joined. In
  general, LINK is the fastest matching operation,
  then LINEAR with an indexed ltrelate_itemgt, and
  then ORDERED. The fastest option, LINK cannot be
  applied to most cases.
• Hints --use the LINEAR (default) option--
  slower but safer --when adding attribute
  data to a coverage, the coverage must be the
  in_file
• --use same name for in_file and
  out_file--otherwise all the associated spatial
  files are not available.
• Note altho. we talk of joining tables, the
  command is JOINITEM. Do not use JOIN, which is a
  very specialized ArcEdit command used for joining
  lines on a map.

31
Connecting Tables with RELATE

• A RELATE temporarily associates data files based
  on a common item occurring in two files.
• Although a relate is temporary, the association
  between files can be saved.
• Types of relates
• One-to-one relate - the values for the common
  item are unique in each file being related
• Many-to-one relate - many records in the main
  file may be matched to one record in the related
  file. Example road types, lookup tables
• Command RELATE establishes or modifies the relate
  environment. Up to 100 relates can be stored in a
  single relate table.
• RELATE ltADDDROPgt add or drop a relate. Will
  enter a dialog to specify properties -- see
  below.
• RELATE ltRESTORE SAVEgt ltinfo_filegt bring back a
  relate from a previous session, or save one
  for a future session
• RELATE LIST relate lists properties of
  either all the relates that are current or
  just the relate you specify

32
Creating a Relate Environment

• RELATE ADD requires the following elements to be
  specified
• Relation name Name to reference the relate
• Table identifier The name of the data file (in
  INFO or other RDBMS) to which you want to relate
• Database name Where the related files is stored
  (e.g. INFO)
• INFO item The item name in the feature
  attribute table that will be matched to the
  relate column. These names do not have to be the
  same
• Related column The item in the related data file
  to match the INFO item
• Relate type Specify the search method Linear,
  Ordered, Link
• Relate access Sets the access rights to the
  related data file. Can be Read/Write (RW),
  Read-Only (RO), or the same as the current file
  (Auto)
• Arc relate add
• Relation Name sorel
• Table Identifier soil (may need to specify full
  path name if other than current directory)
• Database Name INFO
• INFO item soil_type
• Relate column soil_type
• Relate type ordered
• Relate access RW
• Relation Name (starts over -- hit return to end
  addition of relates)

33
Using the Relate Environment

• The relate environment is usable from ARC,
  TABLES, ARCPLOT and ARCEDIT. It is not usable
  from INFO.
• Items out of related files can be used in
  Arc/INFO anywhere that an item name is specified.
• A relate does not store the table from which the
  relate operates therefore, multiple coverages
  can be related to the same data file
• When using ADD, if a relation name already exists
  in the current set of relates, it is replaced by
  the new relate with the same name
• The general form for using fields out of related
  files is
• relation name//INFO item name
• If the INFO data file to which we created a
  relate named SOREL also contains an item called
  distance, we can create a distance buffer
• Usage BUFFER ltin_covergt ltout_covergt
  buffer_item
• Arc buffer soils soilbuf sorel//distance

34
Manipulating the Relate Environment

• RELATE LIST
• Will list out all current relates
• RELATE SAVE ltfile_name.relgt
• Creates a relate file (INFO file) that stores
  relates
• Appends relates to an existing relate file
• Each relate is one record in the relate file can
  store 100 relates in one file
• RELATE RESTORE ltfile_name.relgt
• Establishes the current (active) relate
  environment
• RELATE DROP ltfile_name.relgt
• Drops a relate from all Arc/INFO modules
• Will prompt for relation name to drop typing
  ALL at the Relation Name prompt will drop all
  relates

35
RELATE versus JOIN

• Advantages of RELATE
• Operations on coverages with extended feature
  attribute tables take more time and machine
  resources.
• Can make the updating process easier and faster
  because it keeps descriptive data segregated from
  the spatial data. Can replace the attribute data
  regularly.
• Allows separate departments in an organization to
  access the same coverage while keeping their own
  descriptive data available in separate files.
• Relating data allows you to keep some of your
  data in another RDMBS, such as Oracle.
• Advantages of JOIN
• Simpler for projects of small scope.
• When files are joined, there are fewer files and
  relationships between files to keep track of.