Grouping records in MySQL: group by

Date:

2018-03-19 12:05:40

Views:

575

Rating:

1Like 0Dislike

Share:

Table of contents:

Grouping and analysis of records of your database tables are of practical interest in many applications. The solution of such problems by means of MySQL allows you to perform large volumes of routine work quickly and efficiently.

mysql group by

However, it Should be borne in mind: “purity" of the result will depend on many factors. Design MySQL group by is executed as written by the programmer, but the algorithm may depend on the execution time of the query and the sampling frequency.

Syntax of the grouping operation in the query

In the preparation of request grouping is essential what is selected and how it is grouped. The source table contains a small number of fields, each of which has a different number of unique records. I_status field and w_status equivalent to the first code position, and second, its name. The field record number and time the record was created does not matter.

Author's example is not a picture

This set you can perform bulk operations, for example to determine the maximum and minimum value of a field start_timestamp.

Author's example is not a picture

Similarly, you can formulate a group query to determine all the positions and the number of people employed in them.

Author's example is not a picture

Value MySQL: group by &order by clause can be traced on the queries (i) and (iv) requests (ii) and (iii) are equivalent. But in any given situation should think about how to sort when you perform the grouping operation. In some cases, this can be a problem.

mysql group by order by

Count the number of grouped records is an important consideration when grouping. this operation is mainly used for these purposes, although its use is to identify the different rows in the table in some ways easier, in contrast to the distinct design.

Recommended

How to get out of

How to get out of "Skype" on the "Android" and not only

How to get out of "Skype" "Android"? This question bothers many users. The thing is that the messenger is not so difficult. But there are features that are only for mobile versions. To log out of Skype in this case more difficult than it seems. But i...

Kingo ROOT: how to use the program to gain administrative rights on Android

Kingo ROOT: how to use the program to gain administrative rights on Android

The Gadgets on the platform Android regained the lion's share of the market. Developers are continually perfecting the OS, trying to fit the needs of the users, but from year to year admit palpable mistake: forbid the owner to "stuffing" of his gadge...

How to get from Stormwind to Tanaris: practical tips

How to get from Stormwind to Tanaris: practical tips

World of Warcraft is an iconic MMORPG, uniting millions of players around the world. There are many locations and puzzles, secret trails and larger, but rather dangerous paths. Sooner or later, every player chose the side of the Alliance, we have to ...

Grouping by volume occurrences

You Should note that MySQL group by does not always work against the MySQL order by clause. The question is not so much the priorities of the constructions in the logic of the query itself.

A Query can be formulated as an expression. In the simplest case an expression can consist in counting the number. The use of the MySQL group by count (*) as expression on which grouping is performed.

Author's example is not a picture

Here is the ascending sort order is the value specified in the order by clause.

MySQL does not restrict the programmer in the construction of expressions specifying fields that do not participate in the group, the sequence of grouped elements. But MySQL group by may not work the way the programmer thinks is right.

Multiple grouping

You Can group anything you want, but you should always strive to minimize the number of used fields.

Author's example is not a picture

MySQL group by is a very convenient operation on a duplicate data, it's easy to get the right information, but if the query is grouping multiple fields, it is advisable to consider other options for building a query.

Should take into account that the constructs group by and order by MySQL treats language as a simple "arithmetic" on records. Responsible for operations of grouping options built-in queries, the intelligent use of keys, Union and intersection tables.

mysql group by count

Grouping in the context of the MySQL group by - it is quick getting generalized information, should not be loading the queries with this design deeper meaning. This can lead to unpredictable results and serious amounts of time.


Article in other languages:

AR: https://www.tostpost.com/ar/computers/5231-grouping-records-in-mysql-group-by.html

BE: https://www.tostpost.com/be/kamputary/9300-grupo-ka-zap-sa-mysql-group-by.html

DE: https://www.tostpost.com/de/computer/9301-gruppieren-von-datens-tzen-mysql-group-by.html

ES: https://www.tostpost.com/es/los-ordenadores/9309-agrupar-registros-de-mysql-group-by.html

HI: https://www.tostpost.com/hi/computers/5238-mysql.html

JA: https://www.tostpost.com/ja/computers/5232-mysql.html

KK: https://www.tostpost.com/kk/komp-yuterler/9303-toptastyru-zhazba-mysql-group-by.html

PL: https://www.tostpost.com/pl/komputery/9300-grupowanie-rekord-w-mysql-group-by.html

PT: https://www.tostpost.com/pt/computadores/9295-agrupamento-de-registros-mysql-group-by.html

TR: https://www.tostpost.com/tr/bilgisayarlar/9308-gruplama-kay-tlar-mysql-group-by.html

UK: https://www.tostpost.com/uk/komp-yuteri/9304-grupuvannya-zapis-v-mysql-group-by.html

ZH: https://www.tostpost.com/zh/computers/5695-mysql.html






Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

Comments (0)

This article has no comment, be the first!

Add comment

Related News

Details about how to find location by IP

Details about how to find location by IP

in order to work in the network was in normal mode, it is necessary for each connected node to assign a new ID, which in any case will be unique. As you probably already understood, it is this label called an IP address. In a loca...

How to remove the Chinese program from the computer?

How to remove the Chinese program from the computer?

Sometimes, when downloading any file, with it and downloaded some program for you with strange hieroglyphs. It can be one or more different configurations and types. Many people call this Chinese program.In most cases, these progr...

Recovery and prevention of Winchester: check disk for errors

Recovery and prevention of Winchester: check disk for errors

Often because of improper computer shutdowns, or other failures, errors occur and appear broken sectors on the local hard disk. It is fraught with incorrect downloading of the operating system, information loss and other problems ...

Foursquare - what is it? Foursquare is the app

Foursquare - what is it? Foursquare is the app

Social networks are developing rapidly, offering users new opportunities for communication and exchange of various information. The Foursquare app, in fact, is also a communication platform. What are its functions and what you can...

Details about how the

Details about how the "Instagram" link to "Facebook"

In this article we will see how to bind "Instagram” to “Facebook” through the computer. We will also discuss, why would you need such a bunch of what possibilities it opens up. We will consider two ways of o...

How to remove Yandex bar, if you don't want?

How to remove Yandex bar, if you don't want?

Today we will share with you interesting information about a variety of service from Yandex add-ons in your browsers, no matter which one is installed on your computer. And for those who suddenly wanted to get rid of piling panels...