Using Access to Query Multiple Data Sets (Help Section)

Massachusetts Institute of Technology Department of Urban Studies and Planning 11.204: Planning, Communication & Digital Media Lab 5: Using Access to Query Multiple Data Sets Help Section Exploring MS Access interface and objects Start MS Access To launch MS Access from the Start Menu choose Start > Programs > Microsoft > Microsoft Access. Open An Existing Database In menu File, choose open. In the pop up windows, browse to the folder " the MIT Server\Data\," choose "Cambridge" and click "Open." The main database window opens. In the left lane there is a list of objects; you can find Tables, Queries, Forms, Report and so on. Click each of them to see what is inside in each object category. Examine Tables In the left lane of the Objects list, click "Tables." All the tables in this database are listed on the right of the window. Double click on the table "Cam_geometry" to open it. The table Cam_Geometry" shows in the datasheet view. You can tell the total records number from the bottom status bar. In the tool bar of the main window, click on , the view switch button to switch to the design view. In the upper table, all the fields names and data types are listed. There is a key symbol left to the field "TRACTID," indicating that it is the primary key. You can tell the datatype of the field "Area" from the column "Data Type" in the upper table. Examining Queries Close the table "Cambride_geometry" and go back to the database window. Click "Queries" in the left lane and select the query "qryPopuDensity." Double click it to open it in the datasheet view and click on to switch to design view. There are two tables shown in the upper part of the window, which are linked by a line. The field names in bold font are the primary keys for each table. In the lower part, four fields are listed and all four boxes in the "Show" row are ticked on. Right click on the PopuDense field, in the pop up context menu, choose "Build... ." The expression builder window appears. In the top left of the window, we can see the expression for the field "PopuDense" is "PopuDense: [population]/[area]*2589988.100559." The number "2589988.100559" is used to convert population per square meter to population per square mile. Examining Forms and Reports Close the query, "qryPopuDensity," to return to the database window. Click "Forms" in the left lane and select the form named "frmPopuDensity." Double click to open it. Click the arrow on the bottom of the window, and the record will change accordingly. Close the form to return to the database window. Click "Reports" in the objects list and select "rptPopuDensity." Double click to open it. Close MS Access From menu File, choose "Exit" to close MS Access. Create your own database Create a new database Launch MS Access again and in the menu File, choose "New." In the right task panel, choose "Blank Database." In the new window titled, "File New Database," browse to "H:\private\11.204\lab5," use "yourusername_lab5.mdb" as the file name and click "Create." The empty database file appears as follows, Import data files In the menu file, choose Get External Data > Import. Browse to the folder "the MIT Server\Data\." In the drop down list called "Files of type," choose "Microsoft Excel." Select the file "cambridge_geometry.xls" and click "Import." An data import wizard windows pops up. Choose "Show Worksheets." Only one worksheet "Geometry" is displayed. Click Next. The first row of this table contains the fields names so keep the box ticked on and click Next. Choose "Store the data in a new table" and click Next. Change the name of the first field from "STCNTYTR" to "TractID." In the drop down list called"Indexed" choose "Yes (No Duplicates)." Leave the other field unchanged and click Next. Change to "Choose my own primary key." Select TractID as the primary key and click "Next." Change the table name to "Cam_Geometry" and Click Finish. A message shows the table "Cambridge_geometry" has been imported. In the same way, import the files "MA_gender.xls,""MA_HH.xls,""MA_Popu2k.xls" and "MA_Race.xls" following the directions above. Rename the columns as follows (the opportunity to do this appears on the fourth page of the wizard). { { { { { { { { { P001001: Total Population in 2000 (Name the column as "Popu2000) P015001: Household Units (Name the column as "HHUnits") P012002: Males P012026: Females P003003: White P003004: Black P003005: NatAmer P003006: Asian P003007: Pacific Notice that of the five tables, only "Cambridge_Geometry" has 30 records (the number of tracts in the City of Cambridge). The other four tables contain records for the Commonwealth of Massachusetts, therefore, each contains more than 1,300 records (the number of tracts in MA). Working with tables Modifying Tables In the database window, click "Tables" from the left lane, select "Cam_Geometry" and double click to open it. In menu Edit, choose "Find..." or press Ctrl+F. Type "25017355000" in the "Find What" section. Choose "TractID" as the Look In field and press "Find Next." MS Access locates the record "25017355000." Click on the cell and change the contents to "482491.81312." A pencil icon appears to the left of the record to indicate the change. Press to move to the next record. The pencil icon disappears, showing that the change has been written into the database. Now click "add new record" button . In the TractID field, type "25017354900;" in the area field, type "1285551.80508;" in the perimeter to confirm adding the new record. field, type "5768.48054." Click Two errors in the original table have been corrected. Simple Sorting Go back to the database window, double click on the table called "MA_Popu2k" to open it. Click on the column "Popu2000" to select it. In the menu Record, choose Sort> Sort Descending (or hit ). The table should look like this, The first five records are the most populous Census tracts in Massachusetts. Filtering Tables Open the table "MA_HH." In menu Record, choose Filter>Advanced Filter/Sort. In the first field, choose "HHUnits" and in the criteria row, type ">3000." Then click on the "Apply Filter" button . The filter results are shown in the table. You can observe the number of records on the bottom line of the table. Advance Filtering Go back to the database window and open the table "MA_Gender." In the menu Record, choose Filter>Advanced Filter/Sort. In the first field, choose "Males" and enter ">2500 and <3000" as the criteria. In the second field, choose "females" and enter ">2000 and <2500." Then click on the "Apply Filter" button . Only two records meet these conditions. This example shows how to use the logical operation "AND." Select queries Simple Query Go back to the database window, click on "Queries." From the right side of the window, click "Create queries in design view." In the "Show Table" window, select "MA_Race," click Add then Close. The query design window looks like, Drag TractID from the upper pane to the first field in the lower pane of the window and drag "*" to the second field. Tick off the Show box in the TractID column and leave the box for MA_Race on. Right click the Criteria cell in the TractID column. From the context menu, choose "Build." In the expression builder window, type "[MA_Race]![Black] > [MA_Race]![White]" in the upper blank and press OK. Now we are back to the query design view. In the tool bar, click the "Run" button to execute the query. From the query result window, we can tell that there are 49 Census tracts that meet the condition in V.1 from the bottom line of the window. Save the query as "qryE1." Table Join Go back to the database window, click on "Queries." From the right side of the window, click "Create queries in design view." In the "Show table" window, select two tables "Cam_geometry" and "MA_Race." Since the two tables share one column with the same name and data type--"TractID," MS Access automatically linked them. You can see that they are linked, as shown by the line spanning from one table to the next. In the query design window, drag TractID in the Cam_Geometry table to the first field and "*" in the MA_Race table to the second field. Tick off the Show box in the TractID column, but leave MA_Race* on. Right click the Criteria cell in the TractID column. From the context menu, choose "Build." In the expression builder window, type "[MA_Race]![Black] > [MA_Race]![White]" in the blank space and press OK. Go back to the query design view. In the tool bar, click the "Run" button to execute the query. Only one Census tract in Cambridge meets these conditions. Here, we ran a query against two joined tables. We use the Cam_geometry table to identify which Census tracts are in the City of Cambridge. Save the query as "qryE2." Population Density Start a new query in design view from the database window. Add the two tables for the query -- "Cam_Geometry" and "MA_Popu2k." Drag "TractID" in Cam_geometry table in the upper panel to the first field in the lower panel, "Area" in Cam_geometry table to the second field and "Popu2000" in MA_Popu2k to the third field. Add the fourth field by right clicking the cell and choosing "Build" from the context menu. In the expression builder window, type "PopuDensity: [MA_Popu2k]![Popu2000]/[Cam_Geometry]![AREA]*2589988.100559" in the upper blank and press OK. Tick on the show box in this field. In the tool bar, click the "Run" button to execute the query. You can refine the format of the population density value. Right click the PopuDensity cell in the design view, and choose Property in the context menu. In the field property window, choose "Fixed" as the format and "0" in the decimal place. When we re-run the query, we get, All the values in the population density column are now integers. Save the query as "qryE3." Export Tables Go back to the database window. In the query list, select "qryE3" and open it. In the File menu, choose Export. Browse to H:\private\11.204\lab5, change the save as type to "Microsoft Excel 97-2002."Name it as johndoe_lab5_qryE3.xls (Replace "johndoe" with your username.) and click "Export All." You can check the results by opening the exported file in MS Excel. Created July 2002 by Jinhua Zhao. Updated August 2002 by Lorlene Hoyt. Updated October 2002 by Jinhua Zhao. Updated October 2002 by Lorlene Hoyt. Updated July 2004 by Lorlene Hoyt.