mysql相同内容的字段合并为一条的方法_MySQL
bitsCN.com
从两个表中内联取出的数据，其中category_name字段有相同内容，想将具有相同内容的字段进行合并，将amount字段进行加法运算，变成下表中的内容 
SELECT c.category_name, count(*) AS task_num, sum( t.amount ) AS amount_numFROM cs_witkey_tasks AS t INNER JOIN cs_witkey_category AS c ON t.category_id = c.cidGROUP BY c.category_name DESC 应该用group by而不是order by。 作者 岳冠群 bitsCN.com
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
The difference between counta and count
Nov 20, 2023 am 10:01 AM
The Count function is used to count the number of numbers in a specified range. It ignores text, logical values, and null values, but counts empty cells. The Count function only counts the number of cells that contain actual numbers. The CountA function is used to count the number of non-empty cells in a specified range. It not only counts cells containing actual numbers, but also counts the number of non-empty cells containing text, logical values, and formulas.
How to implement the statement to view table data in MySQL?
Nov 08, 2023 pm 01:40 PM
Title: Statements and specific code examples for viewing table data in MySQL MySQL is an open source relational database management system that is widely used in applications of all sizes. In MySQL, viewing table data is a very basic operation. The following will introduce how to implement this operation through specific statements and code examples. First, we will introduce the statements and specific code examples for viewing table data through the MySQL command line tool. Suppose we have a table named "employees", the following is the pass
What is the usage of count function in php
Sep 09, 2021 pm 05:08 PM
The usage of the count function in PHP is: [count(array,mode);], where the parameter array specifies the array to be counted, and the parameter mode specifies the mode of the function.
Summary of usage differences of MySQL Count function
Nov 29, 2022 pm 04:47 PM
This article introduces to you the usage differences of MySQL’s Count function. The need for statistical data is very easy to encounter in our daily development. MySQL also supports a variety of calculation functions. Next, let’s take a look at the differences between them. , and whether they have some pitfalls.
How to set read-only permissions on a table in Oracle database?
Mar 06, 2024 pm 03:03 PM
In the Oracle database, setting read-only permissions on tables is a very important operation, which can protect data security and prevent misoperations. The following will introduce how to set read-only permissions on tables in an Oracle database and provide specific code examples. First, we need to understand that in the Oracle database, users obtain permissions on tables through authorization. Table permissions include SELECT (query), INSERT (insert), UPDATE (update) and DELETE (delete) operations. Here we will introduce
How does java Count count elements in a stream?
May 11, 2023 pm 04:07 PM
Note 1. Count is a terminal operation that can count the total number of elements in the stream. The return value is of long type. 2. count() returns the count of elements in the stream. This is a special case of induction (an induction operation takes a sequence of input elements and combines them into a summary result by repeatedly applying the combining operation). This is a terminal operation and may have consequences and side effects. After a terminal operation is performed, the pipe is considered consumed and cannot be reused. Example // Verify whether there is a string in the list starting with a, and match the first one, that is, return truebooleananyStartsWithA=stringCollection.stream().anyMatch((s
How to solve the problem of count distinct multiple columns in mysql
Jun 03, 2023 am 10:49 AM
The reproduced test database is as follows: CREATETABLE`test_distinct`(`id`int(11)NOTNULLAUTO_INCREMENT,`a`varchar(50)CHARACTERSETutf8DEFAULTNULL,`b`varchar(50)CHARACTERSETutf8DEFAULTNULL,PRIMARYKEY(`id`))ENGINE= InnoDBAUTO_INCREMENT=1DEFAULTCHARSET=latin1;The test data in the table is as follows. Now we need to count the deduplicated columns of these three columns.
Learn to use the PHP count() function to count the number of array elements
Jun 27, 2023 am 10:37 AM
PHP is a very popular server-side programming language with powerful development capabilities, especially in array operations. Arrays in PHP are widely used to store and manage multiple data items. When operating on an array, it is often necessary to count the number of elements in the array. This can be achieved by using the count() function in PHP. The count() function is PHP's built-in function for counting the number of array elements. When using this function, you only need to pass the array as a parameter of the function
