Page 37-SQL Programming Tutorials: Learn SQL Online-php.cn

Article Tags

All
web3.0
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Backend Development
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Web Front-end
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Database
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Operation and Maintenance
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Development Tools
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
PHP Framework
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Common Problem
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Other
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Tech
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
CMS Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Java
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
System Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Computer Tutorials
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Hardware Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Mobile Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Software Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache
Mobile Game Tutorial
- Mysql Tutorial
- navicat
- SQL
- Redis
- phpMyAdmin
- Oracle
- MongoDB
- NoSQL database
- Memcached
- cloudera
- memcache

Home

Technical Articles

Database

SQL

Explanation on the usage of sum in sql

The SUM function in SQL is used to calculate the sum of a set of values. The syntax is SUM(expression). It is often used in conjunction with a WHERE clause to sum values under specific conditions. The SUM function can be used with the DISTINCT keyword to sum unique values, or with the GROUP BY clause to sum grouped data.

May 02, 2024 am 12:03 AM

聚合函数

How to use sum function in sql

The SUM() function in SQL is used to calculate the sum of numeric columns. It can calculate sums based on specified columns, filters, aliases, grouping and aggregation of multiple columns, but only handles numeric values and ignores NULL values.

May 02, 2024 am 12:01 AM

聚合函数

How to write where statement in sql

The SQL WHERE statement is used to filter rows that meet specific conditions from a table. Its syntax is: SELECT field list FROM table name WHERE conditional expression. Conditional expressions consist of Boolean expressions and Boolean operators (AND, OR, NOT). Boolean expressions usually consist of comparison operators (=, !=, <, <=, >, >=) and operands (table values, subqueries).

May 02, 2024 am 12:00 AM

The role of union in sql

The UNION operator combines rows from multiple tables with the same column structure into a single result set, eliminating duplicate rows and automatically converting data types. 1. Merge rows from different tables; 2. Eliminate duplicate rows; 3. Convert data types to match column structure.

May 02, 2024 am 12:00 AM

排列

How to use modify in sql

The MODIFY command in SQL is used to modify the table structure, including adding columns, deleting columns, modifying column data types, modifying column default values, and modifying whether columns can be null.

May 01, 2024 pm 11:54 PM

How to use join on in sql

JOIN ON is used to match rows between multiple tables by specified columns and return the join results. The steps include: specifying the target table, the join type (INNER, LEFT, RIGHT, FULL) and the join condition (matching columns of both tables in the ON clause).

May 01, 2024 pm 11:51 PM

How to use joinmchno in sql

JOINMCHN0 is a SQL statement used to relate data from different tables through a common column. The steps for its use are: Determine the two tables to be connected. Identify common columns. Write a JOINMCHN0 statement, specifying the tables and common columns to be joined. Execute queries to retrieve related data.

May 01, 2024 pm 11:51 PM

What is used to express conditions in sql

The WHERE keyword in SQL that expresses conditions allows you to filter records by specifying criteria, limiting the data to be retrieved based on specific columns or expression values. WHERE condition types include equality conditions, inequality conditions, comparison conditions, Boolean conditions, null conditions, LIKE conditions, IN conditions, and BETWEEN conditions.

May 01, 2024 pm 11:51 PM

The keywords of query commands in sql are

The command keyword for querying data in SQL is SELECT, which is used to extract specific columns or records from a database table. The SELECT statement structure includes: SELECT [DISTINCT] <Column name to be extracted>FROM <Table name>[WHERE <Filter condition>][ORDER BY <Sort column>][LIMIT <Number of records returned>]

May 01, 2024 pm 11:48 PM

What is the command that expresses query in sql

In SQL, the command to execute a query is SELECT. The syntax of the SELECT statement includes the following components: 1. SELECT <column_list>: Specifies the column to be retrieved; 2. FROM <table_name>: Specifies the table to retrieve data; 3. [WHERE <condition>]: Filters the rows of query results; 4. [GROUP BY <column_list>]: Group the results; 5. [HAVING <condition>]: Filter the grouped results; 6. [ORDER

May 01, 2024 pm 11:48 PM

How to express not equal in sql

The symbols for inequality in SQL are != or <>. The != operator is the most common and is used to find rows that are not equal to a specified value. The <> operator is a synonym for !=. SQL automatically performs type conversions when comparing different data types. The NOT keyword can also be used to indicate not equal to improve code readability. Be careful not to confuse != or <> with =, which is used to check for equality.

May 01, 2024 pm 11:48 PM

Statement representing one character in sql

In SQL, use single quotes (') to represent a single character, with the syntax '[character]. ' Character literals must be enclosed in single quotes and can contain only one character. Special characters can be represented using the escape character (').

May 01, 2024 pm 11:45 PM

Function that represents a character in sql

The functions that represent a single character in SQL are: SUBSTRING: Extract the substring at the specified position (provide a starting position and a length of 1) CHAR: Create a Unicode character (accept Unicode code points) CHR: Create an ASCII character (accept ASCII code points) UNICHAR: Create Unicode characters (accepts character names)

May 01, 2024 pm 11:45 PM

What does arbitrary character represent in sql?

The wildcard character representing any character in SQL is the percent sign (%). It can be placed at the beginning, end, or middle of a pattern string to match characters at the beginning, end, or inclusion of the specified string.

May 01, 2024 pm 11:45 PM