« W3Schools Home Next Chapter » SQL SQL is a standard language for accessing databases. Our SQL tutorial will teach you how to use SQL to access and manipulate data in: MySQL, SQL Server, Access, Oracle, Sybase, DB2, and other database systems....
At W3Schools you will find a complete reference for keywords and functions: SQL Keyword Reference MYSQL Functions SQLServer Functions MS Access Functions SQL Quick Reference SQL Data Types Data types and ranges for Microsoft Access, MySQL and SQL Server. ...
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Any operation performed with NULL results in NULL. Different databases have different functions to handle null. There is a common function that is used in MySQL, Microsoft SQL Server, and Oracle to treat NULLs. SELECT ename, sal+COALESCE(comm,0) FROM employee; Output: ENAME SAL+COALESCE(COMM...
[Advanced] SQL Window Functions [Advanced] SQL Advanced JOINS & Performance Tuning 下面以第一节课为例,老师先是通过视频的形式讲解相关的概念: 美国人嘛,自然语音纯正,听起来也容易,毕竟SQL的内容也不是很难。 再附上清晰的必要文字讲解: 再提供一些知识测试: 加上文字材料: 然后就是必要的query statements...
统计函数 aggregate functions 不能用WHERE语句,可以用于HAVING语句 MAX()SUM()MIN()AVG() 算术 /除法,注意小数位数与除数、被除数中最长的数据类型一致,例如:4/3=1,4.0/3.0=1.333...,4/3.0=1.333...。 ROUND(number, digits) 保留某数字(number)小数点后digits位数 ...
Obviously if the stored procedure language is C#, Java, or R, you’re going to use the functions and syntax of those procedural languages. In other words, despite the fact that the motivation for SQL was to use standardized declarative queries, in the real world you see lots of database-...
1、首先要知道你学的SQL准备应用到哪个数据库,ORACLE、DB2、Sybase、SQL Server、MySQL、MS Access?因为这些数据库中的SQL语句有一些细微的差别; 2、关于资料,只需要:一个网上教程:w3school.com.cn/sql/ind ,买两本书:《SQL必知必会》,《SQL入门经典》。1个网站,2本书,资料足够! 3、停止搜索资料,准备行动,...
Oracle The OracleNVL()function achieves the same result: SELECTProductName, UnitPrice * (UnitsInStock + NVL(UnitsOnOrder,0)) FROMProducts; or we can use theCOALESCE()function, like this: SELECTProductName, UnitPrice * (UnitsInStock +COALESCE(UnitsOnOrder,0)) ...
My SQL / SQL Server / Oracle / MS Access:CREATE TABLE Persons ( City varchar(255) DEFAULT 'Sandnes' ); The DEFAULT constraint can also be used to insert system values, by using functions like GETDATE():CREATE TABLE Orders ( OrderDate date DEFAULT GETDATE() ); ...