如何自学SQL？ - 知乎
SQL直来直去，只要定义必要的输入输出，没有对过程的控制。 了解SQL的大致情况后，我们再来看看如何学？ SQL是所有数据库查询的语言，sql由于本身结构化的特点，非常容易入手。
What does <> (angle brackets) mean in MS-SQL Server?
Nov 8, 2013 · What does <> (angle brackets) mean in MS-SQL Server? Asked 11 years, 8 months ago Modified 3 years, 11 months ago Viewed 80k times
sql - Not equal <> != operator on NULL - Stack Overflow
Apr 14, 2011 · 11 In SQL, anything you evaluate / compute with NULL results into UNKNOWN This is why SELECT * FROM MyTable WHERE MyColumn != NULL or SELECT * FROM MyTable …
sql是什么，通俗的说，太专业听不懂？ - 知乎
SQL是一种用于处理数据的语言，就像我们说的汉语、英语一样，有特定的语法结构，让我们灵活地处理数据。 SQL并不难学，首先得理解 S Q L 三个字母分别代表什么。 Structured Query …
What does the "@" symbol do in SQL? - Stack Overflow
The @CustID means it's a parameter that you will supply a value for later in your code. This is the best way of protecting against SQL injection. Create your query using parameters, rather than …
SQL: IF clause within WHERE clause - Stack Overflow
Sep 18, 2008 · Is it possible to use an IF clause within a WHERE clause in MS SQL? Example: WHERE IF IsNumeric(@OrderNumber) = 1 OrderNumber = @OrderNumber ELSE OrderNumber …
Should I use != or <> for not equal in T-SQL? - Stack Overflow
Apr 6, 2009 · Yes; Microsoft themselves recommend using <> over != specifically for ANSI compliance, e.g. in Microsoft Press training kit for 70-461 exam, "Querying Microsoft SQL …
sql - NOT IN vs NOT EXISTS - Stack Overflow
Which of these queries is the faster? NOT EXISTS: SELECT ProductID, ProductName FROM Northwind..Products p WHERE NOT EXISTS ( SELECT 1 FROM Northwind..[Order Details] od …
sql - ORA-00904: invalid identifier - Stack Overflow
May 17, 2011 · SQL> Oracle SQL allows us to ignore the case of database object names provided we either create them with names all in upper case, or without using double quotes.
How do I perform an IF...THEN in an SQL SELECT?
Sep 15, 2008 · The CASE statement is the closest to IF in SQL and is supported on all versions of SQL Server. SELECT CAST( CASE WHEN Obsolete = 'N' or InStock = 'Y' THEN 1 ELSE 0 END …