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

 1 using System;
 2 using System.Data;
 3 using System.Data.SqlClient;
 4
 5 namespace ConTest.Core
 6 {
 7     public class SqlDBHelper
 8     {
 9         /// <summary>
10         /// 执行查询语句，返回DataSet
11         /// </summary>
12         /// <param name="sSQLString">查询语句</param>
13         /// <returns>DataSet</returns>
14         public static DataSet Query(string sDBConnectionString, string sSQLString)
15         {
16             using (SqlConnection connection = new SqlConnection(sDBConnectionString))
17             {
18                 DataSet ds = new DataSet();
19                 try
20                 {
21                     connection.Open();
22                     SqlDataAdapter command = new SqlDataAdapter(sSQLString, connection);
23                     command.Fill(ds, "ds");
24                 }
25                 catch (System.Data.SqlClient.SqlException ex)
26                 {
27                     throw new Exception(ex.Message);
28                 }
29                 return ds;
30             }
31         }
32
33         /// <summary>
34         /// 执行SQL语句，返回影响的记录数
35         /// </summary>
36         /// <param name="SQLString">SQL语句</param>
37         /// <returns>影响的记录数</returns>
38         public static int ExecuteSql(string sDBConnectionString, string SQLString)
39         {
40             using (SqlConnection connection = new SqlConnection(sDBConnectionString))
41             {
42                 using (SqlCommand cmd = new SqlCommand(SQLString, connection))
43                 {
44                     try
45                     {
46                         connection.Open();
47                         int rows = cmd.ExecuteNonQuery();
48                         return rows;
49                     }
50                     catch (System.Data.SqlClient.SqlException E)
51                     {
52                         connection.Close();
53                         throw new Exception(E.Message);
54                     }
55                 }
56             }
57         }
58     }
59 }

控制台程序

 1 using ConTest.Core;
 2 using System;
 3 using System.Text;
 4 using System.Threading.Tasks;
 5
 6 namespace ConTest
 7 {
 8     class Program
 9     {
10         static void Main(string[] args)
11         {
12             StringBuilder sbSql = new StringBuilder();
13
14             Parallel.For(0, 10, item =>
15               {
16                   try
17                   {
18                       //直接插入
19                       //var i = SqlDBHelper.ExecuteSql(ConstValues.SqlServerDBStr, $" INSERT INTO Users VALUES('12138','Wen',2); ");
20
21                       //经sql判断的插入
22                       var i = SqlDBHelper.ExecuteSql(ConstValues.SqlServerDBStr,
23                       @"
24                     INSERT INTO Users
25                     SELECT '12138' UserId ,'Wen' UserName,2 Age
26                     FROM(SELECT '12138' UserId ,'Wen' UserName,2 Age) A
27                     LEFT JOIN Users B
28                     ON B.UserId=A.UserId
29                     WHERE B.UserId IS NULL
30                     ");
31
32                       sbSql.AppendLine($"True，Line：{i}");
33                   }
34                   catch (Exception ex)
35                   {
36                       sbSql.AppendLine($"False，{ex.Message}");
37                   }
38               });
39
40             Console.WriteLine(sbSql.ToString());
41
42             Console.Read();
43         }
44     }
45 }

静态值

 1 namespace ConTest.Core
 2 {
 3     /// <summary>
 4     /// 静态值
 5     /// </summary>
 6     public  class ConstValues
 7     {
 8         /// <summary>
 9         /// 数据库连接字符串
10         /// </summary>
11         public static string SqlServerDBStr = "data source=.;Initial Catalog=ConTest;integrated security=true;";
12     }
13 }

运行结果

直接插入

经sql判断

结语

实现标题描述