lex->sql_command= SQLCOM_BEGIN; /* READ ONLY and READ WRITE are mutually exclusive. */ if (($3 & MYSQL_START_TRANS_OPT_READ_WRITE) && ($3 & MYSQL_START_TRANS_OPT_READ_ONLY)) { YYTHD->syntax_error(); MYSQL_YYABORT; } lex->start_transaction_opt= $3; } ; 上面是解析 START ...
而真正的数据通过hash散列存放在别的物理空间中。 三、慢SQL MySQL执行原理 解析:词法解析->语法解析->逻辑计划->查询优化->物理执行计划 检查是否存在可用查询缓存结果,如果没有或者缓存失效,则调用mysql_execute_command执行。 执行:检查用户、表权限->表上加共享数据->取数据到query cache->取消共享读锁 慢查...
importmysql.connectordefexecute_transaction(sql_commands):conn=mysql.connector.connect(user='user',password='password',database='dbname')cursor=conn.cursor()try:cursor.execute("BEGIN;")forcommandinsql_commands:cursor.execute(command)cursor.execute("COMMIT;")exceptExceptionase:conn.rollback()print("Er...
属性CommandText通常指定具有有效 FOR XML 子句的 Transact-SQL 语句。 但是,CommandText也可以指定返回包含有效 XML 的数据的ntext语句。 典型BeginExecuteXmlReader查询的格式可以设置为以下 C# 示例中的格式: C# SqlCommand command =newSqlCommand("SELECT ContactID, FirstName, LastName FROM dbo.Contact FOR XML AUT...
lex->sql_command= SQLCOM_BEGIN; /* READ ONLY and READ WRITE are mutually exclusive. */ if (($3 & MYSQL_START_TRANS_OPT_READ_WRITE) && ($3 & MYSQL_START_TRANS_OPT_READ_ONLY)) { YYTHD->syntax_error(); MYSQL_YYABORT; }
private SqlConnection connection; private static string GetConnectionString() { // To avoid storing the connection string in your code, // you can retrieve it from a configuration file. // If you have not included "Asynchronous Processing=true" in the // connection string, the c...
SqlCommand command =newSqlCommand("SELECT ContactID, FirstName, LastName FROM dbo.Contact FOR XML AUTO, XMLDATA", SqlConn); 此方法还可用于检索单行、单列结果集。 在这种情况下,如果返回了多行,该方法EndExecuteXmlReader会将XmlReader附加到第一行的值,并放弃结果集的其余部分。
using (SqlConnection connection = new SqlConnection(connectionString)) { try { SqlCommand command = new SqlCommand(commandText, connection); connection.Open(); IAsyncResult result = command.BeginExecuteReader(); // Although it is not necessary, the following code // displays a counter in the conso...
using System.Data.SqlClient; class Class1 { static void Main() { // This is a simple example that demonstrates the usage of the // BeginExecuteNonQuery functionality. // The WAITFOR statement simply adds enough time to prove the // asynchronous nature of the command. string commandText = "...
lex->sql_command= SQLCOM_BEGIN; /* READ ONLY and READ WRITE are mutually exclusive. */ if (($3 & MYSQL_START_TRANS_OPT_READ_WRITE) && ($3 & MYSQL_START_TRANS_OPT_READ_ONLY)) { YYTHD->syntax_error(); MYSQL_YYABORT; } lex->start_transaction_opt= $3; } ; 上面是解析 START ...