Question

我的要求是从表中删除所有记录，但一个。为此，我正在执行一系列两个不同的sql命令。好像在ssms上它运行正常，但C＃不是

--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();
        }
    }
}

我的qsns

如何在C＃中正确声明sql变量（参见 ClearData 方法）
并且，如何在单个查询字符串中执行多个查询？（如果我这样做的话）

修改

我想出了这个来实现这个目标。但现在还好运。请告诉我该怎么做：

IF OBJECT_ID ( 'uspWageDataByState', 'P' ) IS NOT NULL 
    DROP PROCEDURE uspWageDataByState;
GO

CREATE PROCEDURE uspWageDataByState
    @State NVARCHAR(2)  
AS

    DECLARE @int INT
    SET @int  =  (SELECT COUNT(*) 
    FROM [Test] 
    WHERE [STATE] = @State)

    DELETE TOP (@int - 1 ) 
    FROM [Test]
    WHERE [STATE] = @State;

GO

exec uspWageDataByState 'CO'

Answer 1

我在我的环境中运行了这个代码，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();
                }
            }
        }
    }
}

Answer 2

也许这可以帮助您，使用：

更改您的查询（queryToExec）

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;

如果声明的变量是你可以解决的问题，那不是最好的查询，但是你使用的不是最好的形式：P。

我正在添加0行验证，换句话说，当没有找到数据时，sp崩溃了。

Answer 3

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());

Answer 4

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

以这种方式在 aspnet sqlcommand 和 datareader 中工作

如何在C＃中声明sql变量

4 个答案: