4/14/08 Notes

ISP 121 -- 4/14/08

Reference in Course Documents: Access Tutorial

Why is using Filter usually better than using Find to locate data in an Access table?
Ans: When using find, the format of the field value must be exact, for example 90.0 instead of 90. If the format is not exact, the value might not be found.
Give a reason reason why you might prefer the Text datatype over the Number datatype for a column.
Ans: Values of a field containing Text values can be any string of characters. For example "34544-1002" might be entered as a zip code. This value would not be possible for a Number datatype.
Give a reason why you might prefer the Number datatype over the Text datatype for a column.
Ans: One cannot do arithmetic on Text values. Also, numbers will not sort in numerical order if they are Text values.
In the StateTemperatures Example that you used in Activity 2, how would you create a filter to show all of the rows where the average temperature in January was greater than the average temperature in April?
Ans: Enter January for the field and >[Data].[April] for the Criterion.

Most people that use access find queries preferable to filters:
1. Queries allow you to display a subset of the columns.
2. Queries allow you to display summaries of the data, such as averages, sums, standard deviation, maximum and minimum.
3. Queries can be saved with the database.
Read section L in the Access Tutorial for directions on creating queries.
Example: In the StateTemperatures table, create a query that shows the State, Year, January and April columns. Only show the rows where the January temperature is greater than the April temperature.
Repeat the preceding example, but use the February and April columns.

Go over Section J in the Access Tutorial.
A field cannot contain repeated records, it must contain a single value.
A table cannot contain any data anolamies. A data anolamy occurs when a column depends completely on another column that is not the primary key.
A foreign key is a column that references a primary key in a different table.
To eliminate repeated records or data anolamies, use data normalization. Data normalization means splitting a table into two tables, linked with a foreign key.