在 SQL 视图中添加行数

Question

我正在尝试使用 SQL 视图创建 table。它假设在问题 table 的每一行中添加一列，该列将具有对该问题给出的答案的整数值。这是我目前所拥有的：

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;

我知道这是不对的，但我想不出别的。请帮忙！

Answer 1

这不是创建 table，您正在加入

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 2

我最喜欢的相关子查询计数：

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，加入一个分组依据；

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 列表中的列要么是聚合函数的参数，要么也列在 GROUP BY 子句中。

Answer 3

如果你想计算所有条目，你可以使用这个：

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 视图中添加行数

Add rows count in SQL view

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database

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