SQL Fundamentals: Using Single-Row Functions to Customize Output使用单行函数自定义输出
SQL Fundamentals || Oracle SQL语言
DUAL is a public table that you can use to view results from functions and calculations.
The DUAL table is owned by the user SYS and can be accessed by all users.
It contains one column, DUMMY, and one row with the value X.
SQL Fundamentals || Single-Row Functions || 字符函数 character functions
SQL Fundamentals || Single-Row Functions || 数字函数number functions
SQL Fundamentals || Single-Row Functions || 日期函数date functions
SQL Fundamentals || Single-Row Functions || 转换函数 Conversion function
SQL Fundamentals || Single-Row Functions || 通用函数 General function
Using Single-Row Functions to Customize Output
Oracle SQL supplies a rich library of in-built functions which can be employed for various tasks. The essential capabilities of a functions can be the case conversion of strings, in-string or substring operations, mathematical computations on numeric data, and date operations on date type values. SQL Functions optionally take arguments from the user and mandatorily return a value.
- Describe various types of functions available in SQL
- Use character, number, and date functions in SELECT statements
字符、数字、日期函数
1、SQL Functions
Functions are a very powerful feature of SQL. They can be used to do the following:
Perform calculations on data |
执行数据计算 |
Modify individual data items |
修改单独的数据项 |
Manipulate output for groups of rows |
操纵行组的输出 |
Format dates and numbers for display |
格式化日期和数字进行显示 |
Convert column data types |
转换列数据类型 |
SQL functions sometimes take arguments and always return a value.
SQL有时候接收参数并总是返回一个值.
2、Two Types of SQL Function:
Single-row functions |
单行函数 These functions operate on single rows only and return one result per row. 单行函数只操作单个行并为每一行返回一个结果. - Single row functions are the one who work on single row and return one output per row. For example, length and case conversion functions are single row functions. |
Multiple-row functions |
多行函数 - Multiple row functions work upon group of rows and return one result for the complete set of rows. They are also known as Group Functions. |
3、Single-row functions单行函数
Single row functions
Single row functions can be character functions, numeric functions, date functions, and conversion functions. Note that these functions are used to manipulate data items. These functions require one or more input arguments and operate on each row, thereby returning one output value for each row. Argument can be a column, literal or an expression. Single row functions can be used in SELECT statement, WHERE and ORDER BY clause.
Single-row functions are used to manipulate data items. They accept one or more arguments and return one value for each row that is returned by the query.
(1)特点
Manipulate data items |
操作数据项 |
Accept arguments and return one value |
接收参数并返回一个值 |
Act on each row that is returned |
每一行进行操作 |
Return one result per row |
每一行返回一个值 |
Many modify the data type |
单行函数可以修改数据类型 |
Can be nested |
单行函数可以嵌套 |
Accept arguments that can be a column or an expression An argument can be one of the following:
|
函数接收的参数可以是列名或者表达式
|
(2)、语法
Function_name [(arg1,arg2….)]
(3)、类型
字符函数 character functions |
Accept character input and can return both character and number values. |
数字函数 number functions |
Accept numeric input and return numeric values. |
日期函数 date functions |
Operate on values of the DATE data type (All date functions return a value of the DATE data type except the MONTHS_BETWEEN function, which returns a number) 所有日期函数都返回一个DATE类型的值,除了MONTHS_BETWEEN函数,它返回一个数字. |
转换函数 Conversion function |
Convert a value from one data type to another |
通用函数 General function |
NVL:对空值做处理 NVL2:对空值做处理 NULLIF:对空值做处理 COALESCE CASE DECODE General functions The SELECT query below demonstrates the use of NVL function. SELECT first_name, last_name, salary, NVL (commission_pct,0) FIRST_NAME LAST_NAME SALARY NVL(COMMISSION_PCT,0) |
SQL Fundamentals: Using Single-Row Functions to Customize Output使用单行函数自定义输出的更多相关文章
- Oracle SQL Lesson (3) - 使用单行函数自定义输出
大小写转换函数LOWER('SQL Course') = sql courseUPPER('SQL Course') = SQL COURSEINITCAP('SQL Course') = Sql C ...
- SQL Fundamentals || Single-Row Functions || 转换函数 Conversion function
SQL Fundamentals || Oracle SQL语言 SQL Fundamentals: Using Single-Row Functions to Customize Output使 ...
- SQL Fundamentals || Single-Row Functions || 字符函数 character functions
SQL Fundamentals || Oracle SQL语言 SQL Fundamentals: Using Single-Row Functions to Customize Output使 ...
- SQL Fundamentals || Single-Row Functions || 通用函数 General function || (NVL,NVL2,NULLIF,DECODE,CASE,COALESCE)
SQL Fundamentals || Oracle SQL语言 SQL Fundamentals: Using Single-Row Functions to Customize Output使用单 ...
- SQL Fundamentals || Single-Row Functions || 日期函数date functions
SQL Fundamentals || Oracle SQL语言 SQL Fundamentals: Using Single-Row Functions to Customize Output使 ...
- SQL Fundamentals || Single-Row Functions || 数字函数number functions
SQL Fundamentals || Oracle SQL语言 SQL Fundamentals: Using Single-Row Functions to Customize Output使用单 ...
- SQL Fundamentals || Oracle SQL语言
对于SQL语言,有两个组成部分: DML(data manipulation language) 它们是SELECT.UPDATE.INSERT.DELETE,就象它的名字一样,这4条命令是用来对数据 ...
- 微软BI 之SSIS 系列 - Execute SQL Task 中的 Single Row 与 Full Result Set 的处理技巧
开篇介绍 Execute SQL Task 这个控件在微软BI ETL 项目中使用的频率还是非常高的,也是大部分入门 SSIS 初学者最早接触到的几个控制流控件. 我们通常使用 Execute SQL ...
- SQL Fundamentals: Basic SELECT statement基本的select语句(控制操作的现实列)(FROM-SELECT)
SQL Fundamentals || Oracle SQL语言 Capabilities of the SELECT Statement(SELECT语句的功能) Data retrieval fr ...
随机推荐
- IIS------如何安装IIS
1.打开“控制面板”->“程序”->“打开或关闭Windows功能” 2.如图所示: 3.如图所示: 4.点击确定,配置完成
- Git Step by Step – (7) Git远程仓库(续)
上一篇文章介绍了Git远程仓库的一些使用,但是还是有些东西需要补充一下,所以有了这个续篇. .gitignore 前一篇中,我们介绍了Git的patch功能,当我们生成patch之后,"gi ...
- NFS 简介
一.NFS 简介 1. NFS(Network File System)网络文件系统,它允许网络中的计算机之间通过 TCP/IP 网络共享资源2. NFS 应用场景:A,B,C 三台机器上需要保证被访 ...
- Ansible 使用 Playbook 管理 Nginx 配置文件
前面我们已经安装完 Nginx,但是在日常维护中经常需要修改配置文件,并重新加载配置文件,因此来写一个管理 Nginx 配置文件的 Playbook: [root@localhost ~]$ mkdi ...
- Senium 简介
有时候我们在用 requests 抓取页面的时候,得到的结果可能和在浏览器中看到的不一样,在浏览器中可以看到正常显示的页面数据,但是使用 requests 得到的结果并没有.这是因为 requests ...
- [Cubieboard] Node.js 在 Lubuntu 上安装指南
在 Ubuntu 下安装 Node.js sudo apt-get install python-software-properties python g++ make sudo add-apt-re ...
- 敏感词过滤和XML的创建
今天我慢下来啦,因为这三天没有新的课程学习内容,自己仅仅看啦一些,这让我停下来栖息片刻:说说现在的生活,简单的进行着,每天要奔波着去上课,然后回来,每天都在想怎样学习这个小知识点,大脑也在想怎样解决程 ...
- git切换分支(自记)
git fetch git checkout feature/A4-page
- codeforces水题100道 第七题 Codeforces Round #270 A. Design Tutorial: Learn from Math (math)
题目链接:http://www.codeforces.com/problemset/problem/472/A题意:给你一个数n,将n表示为两个合数(即非素数)的和.C++代码: #include & ...
- Java中遍历字符串toCharArray()和charAt()效率比较
public static void test() { String s = "a"; for(int i = 0; i < 100000; i++) { s += &quo ...