C# 如何在C中声明sql变量

我的要求是从表中删除除一条以外的所有记录。为此，我将执行一系列两个不同的sql命令。似乎在ssms上它可以正常工作，但在C上则不行

--This is what I run on ssms without any issue
DECLARE @int INT;
SELECT @int  =  COUNT(*) 
FROM [Table] 
WHERE STATE = 'CO';

--Delete statement
DELETE TOP (@int - 1 ) 
FROM [Table] ;

public static void ClearData(string state)
{
    const string queryToExec = @"DECLARE @int INT;" +
                               "SELECT @int  =  COUNT(*) " +
                               "FROM [Table] " +
                               "WHERE STATE = @State;" +
                               "DELETE TOP (@int - 1 ) " + //NOTICE THIS LINE
                               "FROM [Table] ";

    List<SqlParameter> param = new List<SqlParameter>()
    {
        new SqlParameter {ParameterName = "@State", SqlDbType = SqlDbType.VarChar, Value = state},
    };

    ExecQuery(queryToExec, param);
}

public static void ExecQuery(string query, List<SqlParameter> paramCollection = null)
{
    using (SqlConnection conn = new SqlConnection(ConnString))
    {
        using (SqlCommand mySqlCom = new SqlCommand())
        {
            mySqlCom.CommandText = query;
            if (paramCollection != null) mySqlCom.Parameters.AddRange(paramCollection.ToArray());
            mySqlCom.Connection = conn;
            conn.Open();
            mySqlCom.ExecuteNonQuery();
        }
    }
}

---

也许这可以帮助您更改查询queryToExec，方法是：

ALTER PROCEDURE uspWageDataByState
@State NVARCHAR(2)  
AS

DELETE TOP 
(CASE 
    (SELECT COUNT(*) FROM [Test] WHERE [STATE] = @State) 
    WHEN 0 THEN 1 
    ELSE (SELECT COUNT(*) FROM [Test] WHERE [STATE] = @State) END -1) 
FROM [Test]
WHERE [STATE] = @State;

如果声明的变量是您可以解决的问题，那么它不是最好的查询，但是您使用的任何形式也不是最好的形式：p

---

我正在添加一个0行验证，换句话说，sp在找不到数据时崩溃。

我已经在我的环境中运行了这段代码，它正在按预期工作

我的框架版本是4.5.51641，我的SQL版本是SQL Server 11.0.2100

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;
using System.Data;

namespace PruebasSQL
{
    class Program
    {
        const string ConnString = @"";

        static void Main(string[] args)
        {
            ClearData("A");
        }

        public static void ClearData(string state)
        {
            const string queryToExec = @"DECLARE @int INT;" +
                                       "SELECT @int  =  COUNT(*) " +
                                       "FROM [Table] " +
                                       "WHERE STATE = @State;" +
                                       "DELETE TOP (@int - 1 ) " + //NOTICE THIS LINE
                                       "FROM [Table] ";

            List<SqlParameter> param = new List<SqlParameter>()
            {
                new SqlParameter {ParameterName = "@State", SqlDbType = SqlDbType.VarChar, Value = state},
            };

            ExecQuery(queryToExec, param);
        }

        public static void ExecQuery(string query, List<SqlParameter> paramCollection = null)
        {
            using (SqlConnection conn = new SqlConnection(ConnString))
            {
                using (SqlCommand mySqlCom = new SqlCommand())
                {
                    mySqlCom.CommandText = query;
                    if (paramCollection != null) mySqlCom.Parameters.AddRange(paramCollection.ToArray());
                    mySqlCom.Connection = conn;
                    conn.Open();
                    mySqlCom.ExecuteNonQuery();
                }
            }
        }
    }
}

---

在单个字符串语句中执行多个查询：

string querystring = "select [yourcolumns] from [yourtable];select [yourvalues] from [yourtables]";
sqlcommand cmd  = new sqlcommand(querystring,yourconnection);
sqlDataReader reader = cmd.executeReader();
do
{
 while(reader.Read())
{
 //get your values here
}
}while(reader.NextResult());

---

这样在aspnet sqlcommand和datareader中工作

最好创建一个存储过程并调用它。@RahulSingh感谢您的建议。我不能在数据库中存储任何东西，老实说，我确信这不是最好的方法。你能给我写一个这两条语句的存储过程吗。我不是一个SQLEXXPert，我需要在我的C代码中做所有的事情。我不能重复这一点——这对我来说很有效。在批处理中声明多个语句是很好的—ORM和数据访问层一直都在这样做，例如在准备sp_executesql时。良好的实践建议转义列[State]，并显式设置cmd.CommandType=Text，但这是默认设置。根据拉胡尔的说法，这个过程也是个好主意。出于兴趣，您是否也希望删除[State]=“co”，否则您将删除所有记录？@Rahussing我创建了您建议的存储专业版，但无法正常工作请告诉我wrong@StuartLC请参阅存储过程。Thanks5=一页中的行数，顺便说一下，您可以将参数添加到页码中，1=页码

string querystring = "select [yourcolumns] from [yourtable];select [yourvalues] from [yourtables]";
sqlcommand cmd  = new sqlcommand(querystring,yourconnection);
sqlDataReader reader = cmd.executeReader();
do
{
 while(reader.Read())
{
 //get your values here
}
}while(reader.NextResult());

DECLARE @PageSize INT = 5, @PageNum   INT = 1
SELECT tickets.ID, tickets.userID FROM tickets WHERE tickets.isActive = 1
OFFSET (@PageNum-1)*@PageSize ROWS FETCH NEXT @PageSize ROWS ONLY