mssql不存在便插入存在不执行操作

前言

参考：https://www.jb51.cc/mssql/76911.html

在mssql中，在记录不存在时插入记录，如果存在则不执行操作

数据库

相关语句

--创建表
CREATE TABLE Users
(
UserId VARCHAR(50) PRIMARY KEY,
UserName NVARCHAR(20),
Age INT NOT NULL
)

--直接插入
INSERT INTO Users VALUES('12138','Wen',2)

--经sql判断的插入
INSERT INTO Users
SELECT '12138' UserId ,'Wen' UserName,2 Age
FROM(SELECT '12138' UserId ,'Wen' UserName,2 Age) A
LEFT JOIN Users B
ON B.UserId=A.UserId
WHERE B.UserId IS NULL

--清空表数据
TRUNCATE TABLE Users

控制台程序测试

sql帮助类

using System;
using System.Data;
using System.Data.SqlClient;

namespace ConTest.Core
{
    public class SqlDBHelper
    {
        /// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name="sSQLString">查询语句</param>
        /// <returns>DataSet</returns>
        public static DataSet Query(string sDBConnectionString, string sSQLString)
        {
            using (SqlConnection connection = new SqlConnection(sDBConnectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    SqlDataAdapter command = new SqlDataAdapter(sSQLString, connection);
                    command.Fill(ds, "ds");
                }
                catch (System.Data.SqlClient.SqlException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }

        /// <summary>
        /// 执行SQL语句，返回影响的记录数
        /// </summary>
        /// <param name="SQLString">SQL语句</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string sDBConnectionString, string SQLString)
        {
            using (SqlConnection connection = new SqlConnection(sDBConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (System.Data.SqlClient.SqlException E)
                    {
                        connection.Close();
                        throw new Exception(E.Message);
                    }
                }
            }
        }
    }
}

控制台程序

using ConTest.Core;
using System;
using System.Text;
using System.Threading.Tasks;

namespace ConTest
{
    class Program
    {
        static void Main(string[] args)
        {
            StringBuilder sbSql = new StringBuilder();

            Parallel.For(0, 10, item =>
              {
                  try
                  {
                      //直接插入
                      //var i = SqlDBHelper.ExecuteSql(ConstValues.SqlServerDBStr, $" INSERT INTO Users VALUES('12138','Wen',2); ");

                      //经sql判断的插入
                      var i = SqlDBHelper.ExecuteSql(ConstValues.SqlServerDBStr,
                      @" 
                    INSERT INTO Users
                    SELECT '12138' UserId ,'Wen' UserName,2 Age
                    FROM(SELECT '12138' UserId ,'Wen' UserName,2 Age) A
                    LEFT JOIN Users B
                    ON B.UserId=A.UserId
                    WHERE B.UserId IS NULL
                    ");

                      sbSql.AppendLine($"True，Line：{i}");
                  }
                  catch (Exception ex)
                  {
                      sbSql.AppendLine($"False，{ex.Message}");
                  }
              });

            Console.WriteLine(sbSql.ToString());

            Console.Read();
        }
    }
}

静态值

namespace ConTest.Core
{
    /// <summary>
    /// 静态值
    /// </summary>
    public  class ConstValues
    {
        /// <summary>
        /// 数据库连接字符串
        /// </summary>
        public static string SqlServerDBStr = "data source=.;Initial Catalog=ConTest;integrated security=true;";
    }
}

运行结果

直接插入

经sql判断

结语

实现标题描述