Mysql 如何在一次查询或往返中在同一个表上选择两次?
好的,下面是我尝试过的代码片段:Mysql 如何在一次查询或往返中在同一个表上选择两次?,mysql,c#-4.0,Mysql,C# 4.0,好的,下面是我尝试过的代码片段: private static void CheckForChanges(MySqlConnection connection) { DateTime hair = DateTime.Parse(SmartStyleDataset.Tables["Hair"].Compute("MAX(lastUpdated)", null).ToString()); DateTime cloths = DateTime.Parse
private static void CheckForChanges(MySqlConnection connection)
{
DateTime hair = DateTime.Parse(SmartStyleDataset.Tables["Hair"].Compute("MAX(lastUpdated)", null).ToString());
DateTime cloths = DateTime.Parse(SmartStyleDataset.Tables["Cloths"].Compute("MAX(lastUpdated)", null).ToString());
DateTime accessories = DateTime.Parse(SmartStyleDataset.Tables["Accessories"].Compute("MAX(lastUpdated)", null).ToString());
DateTime cosmetics = DateTime.Parse(SmartStyleDataset.Tables["Cosmetics"].Compute("MAX(lastUpdated)", null).ToString());
List<String>[] NewRows = { new List<String>(), new List<String>(), new List<String>(), new List<String>() };
using (var command = connection.CreateCommand())
{
connection.Open();
command.CommandText =
"SELECT * "
+ "FROM smartstyle.table_changes_logger "
+ "WHERE Updated > @accessories AND Table = 'accessories' ; "
+ "SELECT * "
+ "FROM smartstyle.table_changes_logger "
+ "WHERE Updated > @cosmetics AND Table = 'cosmetics' ; "
+ "SELECT * "
+ "FROM smartstyle.table_changes_logger "
+ "WHERE Updated > @cloths AND Table = 'cloths' ; "
+ "SELECT * "
+ "FROM smartstyle.table_changes_logger "
+ "WHERE Updated > @hair AND Table = 'hair'";
command.Parameters.Add("@cloths", MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value = cloths.ToString("yyyy-MM-dd HH:mm:ss");
command.Parameters.Add("@hair", MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value = hair.ToString("yyyy-MM-dd HH:mm:ss");
command.Parameters.Add("@accessories", MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value = accessories.ToString("yyyy-MM-dd HH:mm:ss");
command.Parameters.Add("@cosmetics", MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value = cosmetics.ToString("yyyy-MM-dd HH:mm:ss");
using (var reader = command.ExecuteReader())
{
do
{
while (reader.Read())
{
NewRows[0].Add(reader.GetString(1));
NewRows[1].Add(reader.GetString(2));
NewRows[2].Add(reader.GetString(3));
NewRows[3].Add(reader.GetString(4));
}
} while (reader.NextResult());
}
}
}
private static void CheckForChanges(MySqlConnection)
{
DateTime hair=DateTime.Parse(SmartStyleDataset.Tables[“hair”].Compute(“MAX(lastUpdated)”,null.ToString());
DateTime Clots=DateTime.Parse(SmartStyleDataset.Tables[“Clots”].Compute(“MAX(lastUpdated)”,null.ToString());
DateTime accessories=DateTime.Parse(SmartStyleDataset.Tables[“accessories”].Compute(“MAX(lastUpdated)”,null.ToString());
DateTime cosmetics=DateTime.Parse(SmartStyleDataset.Tables[“cosmetics”].Compute(“MAX(lastUpdated)”,null.ToString());
List[]NewRows={new List(),new List(),new List(),new List()};
使用(var command=connection.CreateCommand())
{
connection.Open();
command.CommandText=
“选择*”
+“从smartstyle.table\u更改\u记录器”
+“其中更新>@附件和表=‘附件’;”
+“选择*”
+“从smartstyle.table\u更改\u记录器”
+“其中更新>@化妆品和表='化妆品'
+“选择*”
+“从smartstyle.table\u更改\u记录器”
+“其中更新>@Cloth AND Table='Cloth'
+“选择*”
+“从smartstyle.table\u更改\u记录器”
+“其中更新>@hair AND Table='hair';
command.Parameters.Add(“@cloth”,MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value=cloth.ToString(“yyyy-MM-dd-HH:MM:ss”);
command.Parameters.Add(“@hair”,MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value=hair.ToString(“yyyy-MM-dd-HH:MM:ss”);
command.Parameters.Add(“@accessories”,MySql.Data.MySqlClient.MySqlDbType.Timestamp).Value=accessories.ToString(“yyyy-MM-dd-HH:MM:ss”);
command.Parameters.Add(“@cosmetics”,MySql.Data.MySqlClient.MySqlDbType.Timestamp)。Value=cosmetics.ToString(“yyyy-MM-dd HH:MM:ss”);
使用(var reader=command.ExecuteReader())
{
做
{
while(reader.Read())
{
新行[0]。添加(reader.GetString(1));
新行[1].Add(reader.GetString(2));
新行[2].Add(reader.GetString(3));
新行[3].Add(reader.GetString(4));
}
}while(reader.NextResult());
}
}
}
但是这不起作用,我从mysql中得到以下一般错误,我不明白
您的SQL语法有错误;检查与MySQL服务器版本对应的手册,以了解在“Table=”附件“附近使用的正确语法;从smartstyle.table\u changes\u logger中选择*,其中Upd'位于第1行您需要像表格
那样用反勾号转义
SELECT *
FROM smartstyle.table_changes_logger
WHERE Updated > @accessories
AND `Table` = 'accessories'