MSSQL实现复杂多重条件判断（mssql 多重判断）

SQL Server 是 a popular database server, used by organizations around the world. This comprehensive and powerful system allows organizations to query and analyze data quickly, allowing for greater decision making efficiency. However, sometimes the queries become too complex for SQL Server to handle, as it uses rigid structure, meaning that multi-condition queries must be built carefully.

创新互联公司专注于陵城企业网站建设,响应式网站开发,成都做商城网站。陵城网站建设公司,为陵城等地区提供建站服务。全流程按需网站建设，专业设计，全程项目跟踪，创新互联公司专业和态度为您提供的服务

Fortunately, MSSQL (Microsoft SQL Server) makes it possible to implement complex logic with multiple conditionals. It is done through a T-SQL (Microsoft Transact-SQL), batch of queries, which can be used to create more complex conditionals. The most common way of implementing multiple conditionals is through a case statement.

Let’s take an example of a query to determine the total amount due for a group of customers based on their credit rating. The query would be designed as follows:

“`sql

SELECT

customerID,

(CASE

WHEN creditRating = ‘A’

THEN amountDue * 0.90

WHEN creditRating = ‘B’

THEN amountDue * 0.8

WHEN creditRating = ‘C’

THEN amountDue * 0.7

ELSE

amountDue

END) AS totalAmountDue

FROM

Customer

“`

In the example above, the CASE statement is evaluating the customer’s credit rating and calculating a total amount due based on that information. The case statement is evaluated from top to bottom until the statement that matches the condition is found.

The case statement is a powerful feature in MSSQL, as it enables users to easily implement complex logic with multiple conditions. The flexibility of the case statement gives users the ability to integrate variables and make quick decisions when processing data. It also provides a more organized way of dealing with complex data.

MSSQL also enables users to use variables to store the result of a single CASE statement, avoiding the need to execute multiple CASE statements. This is done by assigning a result to a variable and then using that variable in the same CASE statement.

For example, a query can be written to assign a value to a variable based on a customer’s credit rating, and then use that variable to calculate the total amount due. This can be done using the following code:

“`sql

DECLARE @creditRating varchar(2)

SELECT

@creditRating = Customer.creditRating

FROM

Customer WHERE Customer.customerID = @custID

SELECT

customerID,

(CASE

WHEN @creditRating = ‘A’

THEN amountDue * 0.90

WHEN @creditRating = ‘B’

THEN amountDue * 0.8

WHEN @creditRating = ‘C’

THEN amountDue * 0.7

ELSE

amountDue

END) AS totalAmountDue

FROM

Customer

MSSQL’s case statement is an extremely useful tool for implementing complex logic with multiple conditionals. It provides users with the ability to easily create and save variables, as well as to process and analyze data quickly, aiding in decision making efficiency. Thanks to its flexibility, multi-condition queries can be written in a more organized manner, making them easier to read and understand. 

成都网站推广找创新互联，老牌网站营销公司
成都网站建设公司创新互联(www.cdcxhl.com)专注高端网站建设,网页设计制作,网站维护,网络营销,SEO优化推广,快速提升企业网站排名等一站式服务。IDC基础服务：云服务器、虚拟主机、网站系统开发经验、服务器租用、服务器托管提供四川、成都、绵阳、雅安、重庆、贵州、昆明、郑州、湖北十堰机房互联网数据中心业务。

网页名称：MSSQL实现复杂多重条件判断（mssql 多重判断）
文章转载：http://www.shufengxianlan.com/qtweb/news45/189195.html

网站建设、网络推广公司-创新互联，是专注品牌与效果的网站制作，网络营销seo公司；服务项目有等

广告

声明：本网站发布的内容（图片、视频和文字）以用户投稿、用户转载内容为主，如果涉及侵权请尽快告知，我们将会在第一时间删除。文章观点不代表本网站立场，如需处理请联系客服。电话：028-86922220；邮箱：631063699@qq.com。内容未经允许不得转载，或转载时需注明来源： 创新互联