Question

Into how many types a query can be categorised?Explain them.

Answer 1

Query can be classified in four types Select, Action, Parameter and Aggregate query
Select Query

The select query is the simplest type of query and because of that, it is also the most commonly used one in Microsoft Access databases. It can be used to select and display data from either one table or a series of them depending on what is needed.

In the end, it is the user-determined criteria that tells the database what the selection is to be based on. After the select query is called, it creates a "virtual" table where the data can be changed, but at no more than one record at a time.

Action Query

When the action query is called, the database undergoes a specific action depending on what was specified in the query itself. This can include such things as creating new tables, deleting rows from existing ones and updating records or creating entirely new ones.

Action queries are very popular in data management because they allow for many records to be changed at one time instead of only single records like in a select query.


Parameter Query

In Microsoft Access, a parameter query works with other types of queries to get whatever results you are after. This is because, when using this type of query, you are able to pass a parameter to a different query, such as an action or a select query. It can either be a value or a condition and will essentially tell the other query specifically what you want it to do.

It is often chosen because it allows for a dialog box where the end user can enter whatever parameter value they wish each time the query is run. The parameter query is just a modified select query.

Aggregate Query

A special type of query is known as an aggregate query. It can work on other queries (such as selection, action or parameter) just like the parameter query does, but instead of passing a parameter to another query it totals up the items by selected groups.

It essentially creates a summation of any selected attribute in your table. This can be further generated into statistical amounts such as averages and standard deviation, just to name a couple.

Answer 2

A query is a request for data or information from a database table or combination of tables. ... One of several different query languages may be used to perform a range of simple to complex database queries.