C# SQLite序列操作实现方法详解
1. 简介
本文主要介绍如何使用C#操作SQLite数据库中的序列(sequence),包括创建、查看、增加和删除序列。
2. 创建和查看序列
2.1 创建序列
在SQLite中创建序列需要用到以下SQL语句:
CREATE SEQUENCE sequence_name INCREMENT BY step START WITH start_value MAXVALUE max_value MINVALUE min_value CYCLE NOCYCLE;
其中,sequence_name
代表要创建的序列的名称,step
代表每次递增或递减的值,默认为1,start_value
代表序列的开始值,默认为1,max_value
和min_value
代表序列可以到达的最大值和最小值,默认为最大值为9223372036854775807(64位整数的最大值),最小值为-9223372036854775808(64位整数的最小值)。CYCLE
和NOCYCLE
代表序列是否循环,循环时到达最大值会从最小值重新开始,默认为不循环。
在C#中创建序列可以采用以下方法:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand command = new SQLiteCommand("CREATE SEQUENCE sequence_name INCREMENT BY 2 START WITH 5 MAXVALUE 50 MINVALUE 0 CYCLE", connection);
command.ExecuteNonQuery();
connection.Close();
2.2 查看序列
查看序列可以使用以下SQL语句:
SELECT name, seq, min, max, increment, cycle FROM sqlite_sequence WHERE name='sequence_name';
其中,name
代表序列的名称,seq
代表当前序列的值,min
代表序列到达的最小值,max
代表序列到达的最大值,increment
代表每次递增或递减的值,cycle
代表序列是否循环。
在C#中查看序列可以采用以下方法:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand command = new SQLiteCommand("SELECT name, seq, min, max, increment, cycle FROM sqlite_sequence WHERE name='sequence_name'", connection);
SQLiteDataReader dataReader = command.ExecuteReader();
while (dataReader.Read())
{
Console.WriteLine("Sequence Name: " + dataReader["name"]);
Console.WriteLine("Sequence Value: " + dataReader["seq"]);
Console.WriteLine("Sequence Minimum Value: " + dataReader["min"]);
Console.WriteLine("Sequence Maximum Value: " + dataReader["max"]);
Console.WriteLine("Sequence Increment: " + dataReader["increment"]);
Console.WriteLine("Sequence Cycle: " + dataReader["cycle"]);
}
dataReader.Close();
connection.Close();
3. 增加和删除序列
3.1 增加序列
增加序列可以使用以下SQL语句:
SELECT sequence_name.NEXTVAL FROM dual;
其中,sequence_name
代表要增加的序列名称。
在C#中增加序列可以采用以下方法:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand command = new SQLiteCommand("SELECT sequence_name.NEXTVAL FROM dual", connection);
int sequenceValue = Convert.ToInt32(command.ExecuteScalar());
connection.Close();
3.2 删除序列
删除序列可以使用以下SQL语句:
DROP SEQUENCE sequence_name
在C#中删除序列可以采用以下方法:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand command = new SQLiteCommand("DROP SEQUENCE sequence_name", connection);
command.ExecuteNonQuery();
connection.Close();
4. 示例说明
4.1 示例1:创建和查看序列
下面的示例创建一个名为sequence_test的序列,每次递增2,从5开始,最大值为50,最小值为0,循环:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand createCommand = new SQLiteCommand("CREATE SEQUENCE sequence_test INCREMENT BY 2 START WITH 5 MAXVALUE 50 MINVALUE 0 CYCLE", connection);
createCommand.ExecuteNonQuery();
SQLiteCommand selectCommand = new SQLiteCommand("SELECT name, seq, min, max, increment, cycle FROM sqlite_sequence WHERE name='sequence_test'", connection);
SQLiteDataReader dataReader = selectCommand.ExecuteReader();
while (dataReader.Read())
{
Console.WriteLine("Sequence Name: " + dataReader["name"]);
Console.WriteLine("Sequence Value: " + dataReader["seq"]);
Console.WriteLine("Sequence Minimum Value: " + dataReader["min"]);
Console.WriteLine("Sequence Maximum Value: " + dataReader["max"]);
Console.WriteLine("Sequence Increment: " + dataReader["increment"]);
Console.WriteLine("Sequence Cycle: " + dataReader["cycle"]);
}
dataReader.Close();
connection.Close();
4.2 示例2:增加和删除序列
下面的示例使用已经创建的名为sequence_test的序列,增加序列值和删除序列:
using System.Data.SQLite;
SQLiteConnection connection = new SQLiteConnection("Data Source=D:\\sample.db;Version=3;");
connection.Open();
SQLiteCommand insertCommand = new SQLiteCommand("SELECT sequence_test.NEXTVAL FROM dual", connection);
int sequenceValue = Convert.ToInt32(insertCommand.ExecuteScalar());
Console.WriteLine("Sequence Value: " + sequenceValue);
SQLiteCommand deleteCommand = new SQLiteCommand("DROP SEQUENCE sequence_test", connection);
deleteCommand.ExecuteNonQuery();
connection.Close();
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