Follow these steps to get started: o Launch MS Access from your start menu. The MS Access startup panel is displayed:

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1 Forms-based Database Queries The topic presents a summary of Chapter 3 in the textbook, which covers using Microsoft Access to manage and query an Access database. The screenshots in this topic are from Microsoft Access 2016, which is several releases newer than the Access 2007 version that was used in the textbook. Also, this presentation uses the Horse Owners Association database that is also used in the video demonstration of Microsoft Access that is included in this module. QBE: The Roots of Forms-based Queries A forms-based query language uses a GUI-panel for the creation of a query. An alternative is a command-based query language such as SQL. Experience has shown that both methods are useful to know: o Forms-based queries lend themselves to individuals accustomed the GUI environments. o Command-based queries lend themselves to database users familiar with command syntax, and to programming language modules where database queries need to be embedded in the program code. Getting Started in Microsoft Access A Microsoft Access database is stored using a single data file, which includes all the tables, queries, forms, reports, metadata, and table data. While this hampers scalability, it makes transporting databases from one computer system to another quite easy. The Horse Owners Association database (horse_assn.accdb) may be downloaded here: <John: place download link here> Follow these steps to get started: o Launch MS Access from your start menu. The MS Access startup panel is displayed:

2 o From the startup panel (shown below), click Open Other Files, navigate to where you saved the horse_assn.accdb database file, and click the file name to open It as shown in the following screenshot. o Once the database it open, the Access Home Panel is displayed as shown in the following screenshot. The top part of the panel displays the Home Ribbon, which contains a menu of options. The top line of the ribbon is the Quick Access Toolbar, which allows you to navigate through the various ribbons. The left margin contains the object navigator, which by default, lists the tables in the database (other types of objects can be easily selected).

3 o Here is a closer look at the options on the Home ribbon: o The Create ribbon contains options for creating tables, queries, forms and reports. In this course, we will work only with tables and queries. Forms and reports are out of scope because they are used to build applications using Access, and this course is limited to database concepts. o The External Data ribbon provides options for importing data from and exporting data to data sources outside of MS Access.

4 o The Database Tools ribbon contains a variety of tools for use with Access databases and applications. In this course, we will be using the Relationships tool to manage referential constraints. o The Add-ins ribbon shows extensions to Access that have been installed. Without any add-ins, it is blank (and thus not displayed here). If you click the down-arrow icon on the Object Navigator (along the left-hand margin of the Access window), and select All Access Objects, the navigator will show all object types. As you can see, I included one query named HORSE_LINEAGE along with Tables named HORSE, OWNER, RACE and RACE_RESULT in the sample database. The chevron icons allow you to expand and collapse things within the navigator, including shuttering the navigator to give you more screen space to work in the main part of the Access window.

5 You can right-click objects within the navigator to see a drop-down menu of options that can be selected for the objects, as shown in the following screenshot. The Microsoft Access Relationships Panel Microsoft Access provides the Relationships panel, shown in the following screenshot, for the definition and maintenance of referential constraints between relational tables. To access the Relationships panel, select the Database Tools ribbon, and then the Edit Relationships option. I have expanded and rearranged each of the tables on the panel display so you can see complete column names.

6 Note the following on panel: You can add a table (from those that already exist in the database) by clicking the Show Table icon on the ribbon, which will display a pop-up menu that lists tables in the database selecting a table from the list adds it to the panel. You can remove a table from the panel by clicking on it (on the panel) and then pressing the Delete key on your keyboard. Keep in mind that adding or removing tables from the panel has no effect on the tables themselves tables removed from the panel are still in the database. Each line on the panel represents a relationship (logically) and in most cases, a referential constraint (physically). These relationships assist you when writing queries because they automate table join logic, and as covered in previous modules, referential constraints enforce referential integrity between primary keys and foreign keys. o The symbol 1 at the end of a line represents the one side of the relationship. o The infinity symbol (a sideways 8) at the end of a line represents the many side of the relationship. o Lines with no symbols on either end (like the one between HORSE and RACE_RESULT) represent relationships that are not enforced as referential constraints. In this example the HORSE RACE_RESULT relationship cannot be enforced because there are HORSE_ID values in the RACE_RESULT table that have no corresponding row in the HORSE table. The missing horses are those that are owned by someone who is not a member of the Horse Owners Association. o MS Access implements relationships involving multi-column primary/foreign keys in an odd way, probably because the earliest versions of the product supported only singlecolumn primary keys. Access requires a relationship line for each column included in the key. The relationship between RACE and RACE_RESULT has three lines because there are three columns in the primary key of the RACE table, which appear as foreign key columns in the RACE_RESULT table. o The HORSE table has two recursive relationships, one to establish SIRE_HORSE_ID (the ID of the horse s father) as a foreign key for the HORSE_ID column, and the other to establish DAM_HORSE_ID (the ID of the horse s mother) as a foreign key for the HORSE_ID column. Access won t permit a relationship to be drawn from the HORSE table to itself, but it will let you add the same table to the panel multiple times. The HORSE_1 and HORSE_2 tables don t actually exist in the database they are virtual duplicates of the HORSE table that were added to the panel for the sole purpose of defining the recursive relationships. Deleting a Relationship To delete a relationship shown on the panel, right-click the relationship line and click the Delete option. If you want to try re-creating the relationship between the OWNER and HORSE tables, go ahead and delete it and then follow the directions under Creating and Maintaining Relationships to re-create it. Creating and Maintaining Relationships Relationships are simple to add and maintain using the Relationships panel. To create a relationship:

7 Click on a foreign key column (to select it) and then drag the foreign key column to the primary key column. In this case I dragged OWNER_ID in the HORSE table to OWNER_ID in the OWNER table. The Edit Relationships popup appears as shown. If you have a multi-column key, you will need to select the other primary key and foreign key columns using the blank lines in the popup. If you wish to create a referential constraint for the relationship, click the Enforce Referential Integrity box. Once you have done that, you have the option of also selecting Cascade Update Related Fields if you plan to update primary key values for existing table rows, and/or the Cascade Delete Related Records if you want to be able to delete a parent table row and have the DBMS automatically delete any child rows associated with the parent row. Click the Create button to save the relationship definition. To maintain a relationship, double-click the relationship line to open the Edit Relationships popup. Another way to open the popup is to right-click the relationship line and then select the Edit Relationship option. Click the Close icon (white X on a red background) to close the Relationships panel. The Microsoft Access Table Design View The Table Design view can be accessed by right-clicking a table on the object navigator and selecting the Design View option. The Design View for the HORSE table is shown here:

8 Note the following regarding the Design View: The ribbon changes to a special Design ribbon that contains options related to designing tables. In the upper part of the panel, the columns in the table are displayed using the following fields: o Field Name: The name of the column o Data Type: The Access data type for the column o Description: A description of the column (optional; manually entered) In the lower part of the panel, a series of fields describe the column that is selected in the upper part of the panel (HORSE_ID in the preceding screenshot). The more important of these fields are: o Field Size: The length of the field (number of characters) o Default Value: The default value for the column when no data is supplied o Required: Yes/No as to whether a column value is required (equivalent to NULL / NOT NULL) o Allow Zero Length: Yes/No as to whether an empty string can be stored in the column. o Indexed: Indicates whether the column is indexed as well as whether the index is unique (No Duplicates versus Duplicates Allowed) On the right-hand margin of the panel, the Property Sheet displays properties of the database table. Creating Queries in Microsoft Access Queries in Access closely resemble what other DBMSs call views. (You will learn more about views in the SQL topics that appear later this module.) Access queries do not store any data, but the query definition can be saved as a database object for easy reuse. While there are other methods for creating queries, I think the Query Design View is the most useful.

9 Creating a Query (Query Design View) To create a query, do the following: On the top menu, click Create to switch to the Create ribbon. Click on the Query Design icon. The Query Design View panel is opened and the Show Table dialog box automatically opens. Click on the HORSE table to select it, click Add and then Close (to close the Show Table dialog box). See the following screenshots of the Show Table dialog box, followed by the Query Design View with the HORSE table added.

10 Note the special Design ribbon that is displayed above the Query Design view. The upper part of the panel contains a graphical display of the tables involved in the query. If the query involves joins, lines between the tables show the columns being used to match rows. The lower part of the panel contains the specification for the query, in the form of a template for the rows that will be returned in the query s result set. Each column corresponds with a column in the result set. The rows in the template are used as follows: o Field: The expression that will return data for the corresponding result set column. The simplest form of expression is either a constant or the name of a table column. o Table: The name of the source table for the data in the corresponding result set column (if any). o Sort: Sorting option for the column (Ascending, Descending, Not Sorted, or blank, which is the same as Not Sorted). If multiple columns are sorted, the sequence of the sorts is left to right. The equivalent in SQL is the ORDER BY clause. o Show: Checkbox that selects whether the column appears in the displayed result set. This is useful if you add columns for sorting, filtering, or intermediate calculations that you don t wish to display in the result set. o Criteria: Filtering conditions that select rows from the source tables that will be included in the result set. The equivalent in SQL is the WHERE clause. o or: Any number of additional criteria lines. Conditions placed on the same line are evaluated using a logical AND. The conditions on any additional lines are treated as logical OR conditions. Therefore, a row in the source table is included in the result set if all the conditions on any one of the lines evaluate to a logical TRUE. Columns can be added to the query form using several methods: o Double click the column from the table displayed in the upper part of the form.

11 o o Drag a column from the table display and drop it on a column in the query form. Type the column name, a constant value, or any valid Access SQL expression directly into the query form. Query Criteria Expressions Expressions that filter rows returned by the query are written in a free-form style. They must evaluate to a Boolean TRUE, FALSE, or if missing (null) values are involved, UNKNOWN. Here are some points regarding query expressions: The valid comparison operators are: Operator Description = Equal to < Less than <= Less than or equal to > Greater than >= Greater than or equal to <> Not equal to IS NULL Column value is null IS NOT NULL Column value Is not null LIKE String pattern matching IN Value matches any item in the supplied list or subquery If you write SQL, Access query expressions have some syntax differences you need to know: o Character strings are enclosed in double quotes. (SQL uses single quotes.) o Date strings are enclosed in hash signs (#). (SQL uses single quotes.) o Object names that include spaces are enclosed using square brackets, such as [Owner Full Name]. SQL uses double quotes for so-called quoted identifiers. Frankly, I don t recommend using names that include spaces. Here is a sample query that shows compound expressions to select all mares born on or after 1/1/2010 along with all stallions, followed by the result set. There are many more examples in Chapter 3 of the textbook.

12 Joining Tables Table joins are relatively easy to specify in Access. When you add multiple tables to the Query Design View, the join specification is automatically generated provided you specified the relationship using the Relationships Panel. If the relationship was not specified, you can specify it by dragging and dropping the primary key column from one table to the foreign key column in another. If a table has a multi-column primary key, you must drag and drop each column of the primary key separately. By default, Access performs an outer join, meaning rows that are not matched in both tables drop out and are therefore not displayed in the result set. Here is a simple join query using the HORSE and RACE_RESULT tables. Here is the result set containing 21 rows. There are actually 22 rows in the RACE_RESULT table, but one of them has no matching row in the HORSE table, so it dropped out.

13 The join can be changed to an outer join by double-clicking the line between the tables on the Query Design View to launch the Join Properties dialog box. You can also right click on the line and select Join Properties to get to the same place. The Join Properties dialog box presents three options from which to choose. If you read the wording, they boil down to Inner, Left Outer and Right Outer joins. If we want to select all rows from the RACE_RESULT table regardless of whether there are matching rows in the HORSE table, we want Option 3. However, we need to change the query to select HORSE_ID from the RACE_RESULT table because for the row that does not match the HORSE table, everything coming from the HORSE table will show up as null in the results. Here is the modified query, followed by the results.

14 We can tell that the row for HORSE_ID KY2445 is the one with no matching row in the HORSE table because its HORSE_NAME value is null. Self Joins Joining tables to themselves can be really confusing at first. To join a table to itself in Access, add the table to the query one additional time for each self-join. Each copy of the table will be given a different alias name to be used in the query, much like the behavior of the Relationships Panel. Recall that the HORSE table contains two recursive relationships, one for the horse s father and the other for the horse s mother. Here is a query that joins the HORSE table to itself twice, once to match the horse to its father and again to match to the mother. (You cannot do this with one join because there are two different foreign key columns involved that must be matched to HORSE_ID.) Both queries

15 use a left outer join because many of the horses do not have both the father (sire) and mother (dam) recorded in the HORSE table. You can find this query (HORSE_LINEAGE) in the sample database. Here is the query and the result set. Note the column aliases assigned to the columns that come from HORSE_1 (joined sire rows) and HORSE_2 (joined dam rows). In Access, aliases are written as labels in front of the column expression with a colon to separate the two. Without the aliases, there would be three columns named HORSE_ID and three named HORSE_NAME, and business users would have difficulty figuring out which was which.

16 Aggregate Functions Aggregate functions combine column data from multiple rows into single rows in the result set. In its simplest form, the aggregate function aggregates all the rows in the table that pass any filter criteria, producing a result set with a single row. The most common aggregate functions are as follows: Aggregate Function AVG COUNT MAX MIN SUM Description Calculates the average value for a column Counts the number of rows found in a column Finds the maximum value in a column Finds the minimum value in a column Sums (adds up) the values in a column Here is a simple query that selects the sum, average, minimum value, and maximum value for the PURSE column in the RACE_RESULT table. To toggle the Total row in the Query Design View form on and off, click the Totals icon on the Design ribbon (the one with sigma symbol). The default value for the Total row is Group By (more on that in a moment) use the drop down list to select the desired function for each. As before, I added aliases (labels) to each of the result set columns to display meaningful names in the result set.

17 If we want to see the total purse won by each horse across all races in which the horse ran, we need to select the HORSE_ID along with the sum of the PURSE column. However, we have to be sure we specify Group By for the HORSE_ID column, which tells the DBMS to group the rows in the query results by HORSE_ID and to show one row in the result set for each group. Otherwise, we would be asking the DBMS to show the HORSE_ID for every row in the table, but the sum for each distinct value of HORSE_ID. (The combination does not make logical sense.) Here is the query specification and the results:

18 Access includes very flexible query capabilities. This topic has merely introduced the capabilities. With practice and some research on your own, you can learn a great deal more about it.