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A query is a request for data or information from a database table or combination of tables. This data may be generated as results returned by Structured Query Language (SQL) or as pictorials, graphs or complex results, e.g., trend analyses from data-mining tools.
One of several different query languages may be used to perform a range of simple to complex database queries. SQL, the most well-known and widely-used query language, is familiar to most database administrators (DBAs).
For a machine to understand a request for information in the first place, the query must be written according to a code known as query language. For example, if you go to a bank and ask “Can I have an espresso?” the teller might be puzzled.
SQL represents one of the standard languages used for database management purposes, while MySQL, instead, is the software using that specific language. Although SQL is a fairly universal query language, other commonly used ones include DMX, Datalog and AQL.
The query database feature is equal in necessity to data storage capability. Thus, a number of query languages have been developed for different database engines and purposes, but SQL is by far the most ubiquitous and well-known. In fact, rookie database administrators often are surprised when they learn about the existence of other query languages.
Query languages generate different data types according to function. For example, SQL returns data in neat rows and columns and is very similar to Microsoft Excel in appearance.
Other query languages generate data as graphs or other complex data manipulations, e.g., data mining, which is the deep analysis of information that uncovers previously-unknown trends and relationships between distinct or divergent data. For example, a SQL manufacturing company query may reveal that monthly sales peak in June and July, or that female sales representatives continually outperform male counterparts during holiday months.
A database can be queried by less experienced users who are not trained in a specific query language. Using a pre-defined query written in a special query language to make a request isn’t the only way to request information from a database.
A user might choose available parameters from a default menu that will guide him or her through the search. This is a simple but less flexible method. The system can also provide the user with a default record where a few blank areas can be filled with the fields and value defining the query. This method is called “query by example” (QBE).