Question

我尝试使用SQL视图创建表。它假设在问题表中的每一行添加一列，该列将具有给予该问题的答案的整数值。这就是我到目前为止所做的：

CREATE VIEW [dbo].[Question]
AS
    SELECT 
       COUNT(answer.Id) as 'Answers',
       question.Id,
       question.CreatorId,
       question.Title,
       question.Content,
       question.CreationDate
    FROM 
       Questions AS question 
    JOIN 
       Answers AS answer ON answer.QuestionId = question.Id;

我明白这是不对的，但我无法想到别的。请帮忙！

Answer 1

我最喜欢的相关子查询来计算：

CREATE VIEW [dbo].[Question]
AS
SELECT (select COUNT(*) from Answers
        where QuestionId = question.Id) as 'Answers',
       question.Id,
       question.CreatorId,
       question.Title,
       question.Content,
       question.CreationDate
FROM Questions AS question;

或者，通过;

加入群组

CREATE VIEW [dbo].[Question]
AS
SELECT COUNT(answer.Id) as 'Answers',
       question.Id,
       question.CreatorId,
       question.Title,
       question.Content,
       question.CreationDate
FROM Questions AS question 
JOIN Answers AS answer
ON  answer.QuestionId = question.Id
GROUP BY question.Id,
         question.CreatorId,
         question.Title,
         question.Content,
         question.CreationDate;

请注意，select列中的列是聚合函数的参数，或者也是GROUP BY子句中列出的。

Answer 2

这不是创建表，而是加入

var commandStr= "If not exists (select name from sysobjects where name = 'Customer') CREATE TABLE Customer(First_Name char(50),Last_Name char(50),Address char(50),City char(50),Country char(25),Birth_Date datetime)";

使用（SqlCommand命令= new SqlCommand（commandStr，con）） command.ExecuteNonQuery（）;

你需要这样

Answer 3

如果您要COUNT所有条目，您可以使用此：

CREATE VIEW [dbo].[Question] AS
SELECT COUNT(*) AS amount FROM Questions

如果您需要更复杂的COUNTing（或其他聚合函数），请查看该页面：

http://www.w3schools.com/sql/sql_func_count.asp

在SQL视图中添加行计数

3 个答案: