What is and how to use a Query – WAU

Understand what Query is and the reasons why using this feature, for the customization of your CMS, can change the experience of customers on your blog and the visibility of your brand on the Internet.

Do you know what Query is? In English, it means question, consultation or doubt. It is a request for information made to the database. which returns a table or a set of them, figures, graphs or complex results.

Various query languages ​​can be used, from the simplest to the most complex. The goal is to analyze trends and define patterns for decision making.

In addition, the feature helps to improve the user experience of your WordPress sitebecause it allows you to make strategic changes, such as highlighting posts related to a certain category on the home page, reducing or increasing the number of type posts per page.

Check out what Query is and some important information to expand your knowledge in the management of relational databases! In this article, you will follow the topics:

What is a Query

The best known language for Queries is Structured Query Language (SQL) and, because it is more familiar to most database administrators (DBAs – DataBase Administrators), it is a widely used option for this purpose.

The extremely usability component also allows the user to insert, update, select and delete records. In a simpler interpretation, they are commands that, when executed, return with information already stored, which can be accessed at any time if the user asks the correct question (command).

How a Query Works

As we said, the most widely used language in Query for querying the database is SQL, even the newest database administrators are surprised to discover that there are other forms of query, just like the native children of a country. are perplexed when hearing a foreign language for the first time.

Each query language returns different types of data, according to the function used. For example, with SQL programs interact with a relational database and generate information organized in rows and columns – a table similar to the appearance of Microsoft Excel.

There are also some languages ​​that return data in the form of graphics. In data mining, the application of this information allows a deep analysis of trends and relational situations between similar or divergent values.

For example, Query in a shoe company’s database may reveal a peak or deficit in sales to delimit periods of seasonality or show the performance of female sales representatives in relation to men.

There is also the possibility of Query for example (QBE – Query By Example), a query method implemented in most relational database systems.

Created in the 1970s, in parallel with the development of SQL, this graphical query language allows users to insert commands into a table, with example elements.

Therefore, it allows users to search for information in tables and fields, as it provides an interface in which the user can insert an example of the data he wants to access. Thus, the data returned is similar to those used as a basis for consultation.

In the background, the user’s Query is transformed into a database manipulation language, such as SQL, and it is this SQL statement that will be executed in the background.

What are the commands of a Query

Let’s say you are not a database administrator or programmer. At that moment, when you already know what Query is, you certainly wonder how a Query works in practice.

The SQL it’s not a programming language, but works as one in creating tables, querying and manipulating information in relational databases. Here are some commands that can be used to create Queries.

Onde

Specifying the data source is the first step in creating tables. This is the initial command, which searches for information in a file or part of memory where the data is stored.

With the Where command, it is possible to search for existing information in another table, for example. Therefore, it is necessary to know the name of the file in which the data is located.

Suppose this file was stored under the name SUPPLIERS. When writing the correct command, the information corresponding to that request is retrieved into memory. Then, we execute the data display command:

Query1.SQL.Text := 'Select * from FORNECEDORES where Codigo = 20';
Query1.Open;

Thus, the lines that really make sense for the table in which you want to analyze are filtered, since only the values ​​that return true will be rescued.

Group by

It is also possible nest the information retrieved from the source table through some rules. For example, we can group the data in the table we created by the name of the company’s suppliers. Just write the Group by command and use the column header as a reference.

If the column with the name of the suppliers is called name, the command will be:

Query1.SQL.Text := group by nome;

Thus, the data will be listed according to the imposed grouping rule.

FieldByName

Now, if we want to select supplier No. 25 from the table to view specific data, for example, we can use the FieldByName method. Suppose the data sought is the address of that supplier:

ShowMessage('Endereço:'+Query1.FieldByName('Endereço').AsString);

AsString means that the information returned will be a word and not a numeric value.

Having

When collecting data, it is also possible to use the having command, so that the result returns only values ​​with that specific filter. However, we can only use this command after the grouping (group by) takes effect.

Fields

Another option is to use the Fields command, which lists the fields in ascending order and also allows the DBA to access the data by its position in Query.

Query1.SQL.Text := ‘Select COUNT(*) from FORNECEDORES where cidade = 'Belo Horizonte’;
Query1.Open;
ShowMessage(Query1.Fields[2].AsString);

In the example, field number two is the supplier position returned by Query. Likewise, we can access any Query field by position:

ShowMessage('Endereço:' + Query1.Fields[5].AsString);
ShowMessage('Nome:' + Query1.Fields[3].AsString);

Despite the functionality of Fields, the FieldByName command references the fields by their name and makes the source code more readable, especially if the query returns many different fields, which can be confusing for analysis.

Order by

Order by is also a simple command, which works to effect the ordering of data according to a pre-established criterion. It works like group by, but instead of just grouping, it adds an extra organizational factor to Query.

While

The while is a loop used to query several records simultaneously. The process is continued as long as the value satisfies the condition and returns true.

Query1.SQL.Text := 'Select * from FORNECEDORES';
Query1.Open;

With this command we select all the records in the SUPPLIERS table. A new table can be filled with the pertinent information, but first it is necessary to activate a loop of repetition so that all the lines of the table are analyzed. An instruction allows starting from the first record:

Query1.First;

We also need to enter the condition of the loop. Eof means End of File or last record, that is, as long as the last line is not analyzed, the looping does not end. The information is listed in a new table, which we will call NOVATABELA:

While not (Query1.Eof) do
NOVATABELA.Items.Add(Query1.FieldByName('Endereço').AsString);

The next command allows data to be passed through while:

Query1.Next;

It is also necessary to end the loop, with the insertion of the command end and then Query1.Close, so that Query is closed. See how the final code looks like below:

Query1.SQL.Text := 'Select * from FORNECEDORES';
Query1.Open;
Query1.First;
While not (Query1.Eof) do
begin
NOVATABELA.Items.Add(Query1.FieldByName('Endereço').AsString);
Query1.Next;
end;
Query1.Close;

Why use Query in WordPress

WordPress (WP) is a CMS (Content Management System), that is, a content management system. For this reason, querying information should also be a feature of the tool.

Do you know how to create a website but don’t know how to manage it? In WP we call the queries WP_Query. Some functions in WordPress like is_home or is_search are basically Queries. They support several parameters in the data architecture, which include:

  • post types;
  • metadata;
  • taxonomy;
  • dates;
  • other custom parameters.

For any post request, for example, WordPress returns the data based on the interpreted arguments. Query defines the content that will be displayed on a page, for example.

We can modify Query to:

  • mask posts from a certain category on the home page;
  • reduce or increase the number of type posts per page;
  • delimit related content;
  • direct the user to a Landing Page;
  • select exclusive content from a category;
  • insert posts published after what is being displayed;
  • sort posts for example.

We need to know the code structure of a Query so that the manipulation in WordPress allows the development of more attractive pages to users in your CMS.

Only through this customization is it possible to create a UX-based site – User Experience – that favors a more complete and targeted browsing experience for your target audience’s sales funnel.

Maintaining an intuitive blog with relevant content to satisfy your customers’ searches is the first step to ensure its relevance and visibility on the Internet.

Furthermore, knowing what Query is allows you to prevent your users from encountering navigation errors that damage your website’s credibility, such as error 404, which occurs when your blog rules are changed.

Keep up with your knowledge of WordPress and know why you should use this CMS in your Content Marketing strategy!