int mysql_stmt_execute(MYSQL_STMT *stmt)

描述

mysql_stmt_execute()执行与语句句柄相关的预处理查询。在该调用期间,将当前绑定的参数标记符的值发送到服务器,服务器用新提供的数据替换标记符。

如果语句是UPDATEDELETEINSERT,通过调用mysql_stmt_affected_rows(),可发现更改、删除或插入的总行数。如果这是诸如SELECT等能生成结果集的语句,调用任何其他能导致查询处理的函数之前,必须调用mysql_stmt_fetch()来获取数据。关于如何获取结果的更多信息,请参见25.2.7.11节,“mysql_stmt_fetch()”

对于生成结果集的语句,执行语句之前,可通过调用mysql_stmt_attr_set()请求mysql_stmt_execute()为语句打开光标。如果多次执行某一语句,在打开新的光标前,mysql_stmt_execute()将关闭任何已打开的光标。

返回值

如果执行成功,返回0。如果出现错误,返回非0值。

错误

·         CR_COMMANDS_OUT_OF_SYNC

以不恰当的顺序执行了命令。

·         CR_OUT_OF_MEMORY

内存溢出。

·         CR_SERVER_GONE_ERROR

MySQL服务器不可用。

·         CR_SERVER_LOST

在查询过程中,与服务器的连接丢失。

·         CR_UNKNOWN_ERROR

出现未知错误。

示例:

在下面的示例中,介绍了使用mysql_stmt_init()mysql_stmt_prepare()mysql_stmt_param_count()mysql_stmt_bind_param()mysql_stmt_execute()、以及mysql_stmt_affected_rows()创建和填充表的方法。假定mysql变量具有有效的连接句柄。

#define STRING_SIZE 50
 
#define DROP_SAMPLE_TABLE "DROP TABLE IF EXISTS test_table"
#define CREATE_SAMPLE_TABLE "CREATE TABLE test_table(col1 INT,\
                                                 col2 VARCHAR(40),\
                                                 col3 SMALLINT,\
                                                 col4 TIMESTAMP)"
#define INSERT_SAMPLE "INSERT INTO test_table(col1,col2,col3) VALUES(?,?,?)"
 
MYSQL_STMT    *stmt;
MYSQL_BIND    bind[3];
my_ulonglong  affected_rows;
int           param_count;
short         small_data;
int           int_data;
char          str_data[STRING_SIZE];
unsigned long str_length;
my_bool       is_null;
 
if (mysql_query(mysql, DROP_SAMPLE_TABLE))
{
  fprintf(stderr, " DROP TABLE failed\n");
  fprintf(stderr, " %s\n", mysql_error(mysql));
  exit(0);
}
 
if (mysql_query(mysql, CREATE_SAMPLE_TABLE))
{
  fprintf(stderr, " CREATE TABLE failed\n");
  fprintf(stderr, " %s\n", mysql_error(mysql));
  exit(0);
}
 
/* Prepare an INSERT query with 3 parameters */
/* (the TIMESTAMP column is not named; the server */
/*  sets it to the current date and time) */
stmt = mysql_stmt_init(mysql);
if (!stmt)
{
  fprintf(stderr, " mysql_stmt_init(), out of memory\n");
  exit(0);
}
if (mysql_stmt_prepare(stmt, INSERT_SAMPLE, strlen(INSERT_SAMPLE)))
{
  fprintf(stderr, " mysql_stmt_prepare(), INSERT failed\n");
  fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
  exit(0);
}
fprintf(stdout, " prepare, INSERT successful\n");
 
/* Get the parameter count from the statement */
param_count= mysql_stmt_param_count(stmt);
fprintf(stdout, " total parameters in INSERT: %d\n", param_count);
 
if (param_count != 3) /* validate parameter count */
{
  fprintf(stderr, " invalid parameter count returned by MySQL\n");
  exit(0);
}
 
/* Bind the data for all 3 parameters */
 
memset(bind, 0, sizeof(bind));
 
/* INTEGER PARAM */
/* This is a number type, so there is no need to specify buffer_length */
bind[0].buffer_type= MYSQL_TYPE_LONG;
bind[0].buffer= (char *)&int_data;
bind[0].is_null= 0;
bind[0].length= 0;
 
/* STRING PARAM */
bind[1].buffer_type= MYSQL_TYPE_STRING;
bind[1].buffer= (char *)str_data;
bind[1].buffer_length= STRING_SIZE;
bind[1].is_null= 0;
bind[1].length= &str_length;
 
/* SMALLINT PARAM */
bind[2].buffer_type= MYSQL_TYPE_SHORT;
bind[2].buffer= (char *)&small_data;
bind[2].is_null= &is_null;
bind[2].length= 0;
 
/* Bind the buffers */
if (mysql_stmt_bind_param(stmt, bind))
{
  fprintf(stderr, " mysql_stmt_bind_param() failed\n");
  fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
  exit(0);
}
 
/* Specify the data values for the first row */
int_data= 10;             /* integer */
strncpy(str_data, "MySQL", STRING_SIZE); /* string  */
str_length= strlen(str_data);
 
/* INSERT SMALLINT data as NULL */
is_null= 1;
 
/* Execute the INSERT statement - 1*/
if (mysql_stmt_execute(stmt))
{
  fprintf(stderr, " mysql_stmt_execute(), 1 failed\n");
  fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
  exit(0);
}
 
/* Get the total number of affected rows */
affected_rows= mysql_stmt_affected_rows(stmt);
fprintf(stdout, " total affected rows(insert 1): %lu\n",
                (unsigned long) affected_rows);
 
if (affected_rows != 1) /* validate affected rows */
{
  fprintf(stderr, " invalid affected rows by MySQL\n");
  exit(0);
}
 
/* Specify data values for second row, then re-execute the statement */
int_data= 1000;
strncpy(str_data, "The most popular Open Source database", STRING_SIZE);
str_length= strlen(str_data);
small_data= 1000;         /* smallint */
is_null= 0;               /* reset */
 
/* Execute the INSERT statement - 2*/
if (mysql_stmt_execute(stmt))
{
  fprintf(stderr, " mysql_stmt_execute, 2 failed\n");
  fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
  exit(0);
}
 
/* Get the total rows affected */
affected_rows= mysql_stmt_affected_rows(stmt);
fprintf(stdout, " total affected rows(insert 2): %lu\n",
                (unsigned long) affected_rows);
 
if (affected_rows != 1) /* validate affected rows */
{
  fprintf(stderr, " invalid affected rows by MySQL\n");
  exit(0);
}
 
/* Close the statement */
if (mysql_stmt_close(stmt))
{
  fprintf(stderr, " failed while closing the statement\n");
  fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
  exit(0);
}

注释:关于使用预处理语句函数的完整示例,请参见文件tests/mysql_client_test.c。该文件可从MySQL源码分发版获得,或从BitKeeper源码仓库获得。