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。

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

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 WHERE MyColumn <> NULL gives you 0 results. To provide a check for NULL values, isNull function is provided. Moreover, you can use the IS operator as you used in the third query.

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 Language，简写为SQL，意思是结构化查询语言。也就是说SQL是用来查询数据用的，通过代码指令来实现个性化的数据抽取 ...

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 concatenating strings and variables. The database engine puts the parameter value into where the placeholder is, and there is zero chance for SQL injection.

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 Server", they say "As an example of when to choose the standard form, T-SQL supports two “not equal to” operators: <> and !=. The former is standard and the latter is not.

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 LIKE '%' + @

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 WHERE p.

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 AS bit) as Saleable, * FROM Product You only need to use the CAST operator if you want the result as a Boolean value. If you are happy with an int, this works: SELECT CASE WHEN …

Jun 19, 2010 · When dealing with big databases, which performs better: IN or OR in the SQL WHERE clause? Is there any difference about the way they are executed?