Compact and Repair:
The developers of Microsoft Access recommend that the database be Compacted and Repaired frequently. Database size is reduced and performance is improved after compacting, and certain types of errors are fixed by repairing.
You can use the Event Scheduler to perform automated, periodic compact and repairs, or use the Maintenance form to do it on demand. To learn even more about compact/repair, close this help screen, press F1, select the index tab, and type 'compact' (without the quotes, of course).
For yet more information, read the Microsoft Technical notes about the Jet Engine Patch and Compacting. NOTE: these articles may be updated or superseded by other articles. Visit the Microsoft Support the get the latest information.
Defrag:
Running the disk defragmenter is said to improve the performance of your hard disk, ostensibly by rearranging data on your hard drive to cause the drive head to move as little as possible when opening files, and by removing gaps from deleted files and putting all the files at the 'beginning' of your hard disk. To learn even more about defrag, press the windows 'Start' menu button, select Help, and enter defrag.
You can use the Event Scheduler to perform automated, periodic disk defragmentations.
Fields, Tables, and Records
Consider a simple table describing customers, which consists of columns for different types of information, such as last name, first name, address, etc. A field is equivalent one column. A record (equivalent to a row) is composed of fields. A given field in a given table always contains the same type of information. This discipline makes it easier to keep your data organized and searchable. Of course one can always define a field that may contain any random data; but if it isn't used consistently it is of little value in analysis. You can refer to a field in a table in queries by using TableName.FieldName, TableName![FieldName], or TableName("FieldName"), for example Customers.LastName.
Filters:
You would probably tend to use Filters on the Customer Form. You select the Filter Icon on the toolbar or from the menu. You can then, using a Query-Like user interface, specify how you would like the form sorted, as well as any record exclusion criteria; e.g. only select last names beginning with the letter 'G'. You should use the help that comes with Microsoft Access for more information on Filters.
Forms:
Forms consist of one or more of the following components:
- A control box which has three buttons:
- Click the square to maximize the form, causing it to fill the entire Microsoft Access window.
- Click the underline to minimize the form, causing it to become a small icon on the bottom of the Microsoft Access window
- Click the X to close the form.
- A Header: generally containing column titles
- Form details: either field names and field edit boxes, or just edit boxes.
- A Footer: generally containing buttons, or summary information.
SatTracker uses forms extensively as the means by which you enter information into the database. Forms are used rather than tabular views because forms give SatTracker more error validation of what you enter, and allow SatTracker to perform hidden tasks to make the database work correctly.
Joins:
As mentioned in Relationships, relational databases are rarely used with simple, flat tables. Joins are used to specify how one table is related to another. The beauty of using joins is, the way tables go together is not specified when they are defined, but instead when the join is made. Of course, in designing a database one should consider how the tables are related so that performance is optimized. Yet, there is still a nice flexibility in this method.
Pathnames:
A pathname consists of a drive letter, one or more directories, and a file name (with an extension); in the form "D:\Path1\Path2\FileName.ext", for example "C:\Sat Tracker\SatTracker.mdb" is the full path name of the main SatTracker database. The extension is very important because it tells Windows the file type, so when you double click the file it knows what application to launch.
Query:
A query is a view of one or more tables. There are several types of queries:
- Select: where a datasheet is displayed for viewing
- Delete: where records are deleted from an underlying table
- Append: where records from the query are appened to another table
- Update: where records in a table are updated to a specific value, perhaps from another table
- MakeTable: where a new table is made whose definition is that of the fields in the query.
Other aspects of queries include:
- The set of tables that makes up the query. If more than one table is used, join is used to specify how the tables are related to each other.
- Which fields in which tables are displayed.
- Selection criteria that applies to the fields, such as only payments greater than 100 dollars.
- How the query is sorted (the order in which the data is displayed).
If you are interested in how queries work, or need them to perform tasks, now would be a good time to consult the Microsoft Access help for more information.
Relationships:
A relational database has a nice paradigm to allow data to be organized in a way that minimizes data redundancy. The database consists of tables, or lists of information. The tables are related to each other using key fields (unique identifiers). For example, to keep service records on a customer, rather than re-entering the customer information for each service record, instead you give each customer an ID, and put the ID in each service record. If you used a 'flat-file' organization, you would have the problem of 'how many service records shall I allow a customer to have?', customer records that are sparsely populated (e.g. space is allocated for up to 10 service records, but many customers have no service at all). With a relational database, each customer can have a practically unlimited number of service records, and it takes up only the amount of space necessary. It also makes searching easier. In a flat file organization, if the customers were being searched for particular types of service, a search entry would have to be made in each instance of a service record. With a relational database, you simply specify the value of the key field to search (e.g Customer ID), and the type of item to search for (e.g. product name = "Local Antenna").
Most of the tables in SatTracker relate back to the Customer Table using the CustomerId, and to the OrderTable using the CustomerId and OrderDate.
Scandisk:
Run Scandisk to repair errors in the Windows disk operating system caused by abnormal program terminations or poorly behaved applications. It is important to keep the disk free of errors when using Microsoft Access databases. To learn even more about scandisk, press the windows 'Start' menu button, select Help, and enter scandisk.
You can use the Event Scheduler to perform automated, periodic disk scans.
Have Questions? Email Us !