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我正在使用MYSQL C API準備好的語句，並且遇到截斷問題。 mysql_stmt_fetch()總是返回MYSQL_DATA_TRUNCATED，我不明白爲什麼。有人可以告訴我爲什麼數據會被截斷以幫助我解決這個問題嗎？我能想到的唯一原因是如果我的緩衝區變量不是正確的類型，但我認爲它們是正確的類型。如果你有興趣，我使用的代碼如下。我還展示了我的表格及其結構的副本，我直接從MYSQL客戶端的命令中獲取。用C api解決MYSQL截斷問題
關於代碼的一些注意事項：
我已經修改了它打印出來的值，即使它返回截斷數據。當我這樣做時，第一個字段似乎打印正確，但浮動字段和日期時間字段是亂碼。另外，它似乎讀取正確的行數。
大部分代碼錯誤檢查各種函數調用。這些錯誤檢查都不會被觸發 - 或者至少它們中的任何一個都不會像您期望的那樣打印出郵件。唯一的錯誤指示是獲取調用返回的MYSQL_DATA_TRUNCATED值。
詳細說明測量表：
+------------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+-------+
| nodeId | int(11) | NO | PRI | NULL | |
| recordtime | datetime | NO | PRI | NULL | |
| slevel | float | YES | | NULL | |
+------------+----------+------+-----+---------+-------+
電流測量表的內容：
+--------+---------------------+--------+
| nodeId | recordtime | slevel |
+--------+---------------------+--------+
| 1 | 2015-09-22 19:33:50 | 2 |
| 1 | 2015-09-24 21:10:20 | 2 |
| 2 | 2015-09-22 19:33:53 | 5 |
| 3 | 2015-09-22 19:33:55 | 2 |
| 3 | 2015-09-22 19:45:42 | 4 |
| 3 | 2015-09-24 21:12:12 | 2 |
| 3 | 2015-09-24 21:13:30 | 3.4 |
| 4 | 2015-09-22 19:33:57 | 7 |
| 4 | 2015-09-24 21:05:53 | 5 |
| 4 | 2015-09-24 21:07:27 | 3 |
| 4 | 2015-09-24 21:22:52 | 9.9 |
| 4 | 2015-09-24 21:35:53 | 5 |
| 6 | 2015-09-24 21:26:01 | 2.2 |
| 6 | 2015-09-24 21:28:15 | 5.4 |
+--------+---------------------+--------+
14 rows in set (0.00 sec)
我的代碼：
static void select_rows (MYSQL_STMT *stmt){
char *stmt_str = "SELECT nodeId, recordtime, slevel FROM Measurements";
MYSQL_BIND param[3];
int my_int;
float my_float;
MYSQL_TIME my_datetime;
my_bool is_null[3];
if (mysql_stmt_prepare (stmt, stmt_str, strlen (stmt_str)) != 0){
print_stmt_error (stmt, "Could not prepare SELECT statement");
return;}
if (mysql_stmt_field_count (stmt) != 3){
print_stmt_error (stmt, "Unexpected column count from SELECT");
return;}
memset ((void *) param, 0, sizeof (param)); /* zero the structures */
/* set up INT parameter */
param[0].buffer_type = MYSQL_TYPE_LONG;
param[0].buffer = (void *) &my_int;
param[0].is_unsigned = 0;
param[0].is_null = &is_null[0];
/* set up FLOAT parameter */
param[1].buffer_type = MYSQL_TYPE_FLOAT;
param[1].buffer = (void *) &my_float;
param[1].buffer = (void *) &my_float;
param[1].is_null = &is_null[1];
/* set up DATETIME parameter */
param[2].buffer_type = MYSQL_TYPE_DATETIME;
param[2].buffer = (void *) &my_datetime;
param[2].is_null = &is_null[2];
if (mysql_stmt_bind_result (stmt, param) != 0){
print_stmt_error (stmt, "Could not bind parameters for SELECT");
return;}
if (mysql_stmt_execute (stmt) != 0){
print_stmt_error (stmt, "Could not execute SELECT");
return;}
if (mysql_stmt_store_result (stmt) != 0){
print_stmt_error (stmt, "Could not buffer result set");
return;}
else{
printf ("Number of rows retrieved: %lu\n",
(unsigned long) mysql_stmt_num_rows (stmt));}
int ii = mysql_stmt_fetch (stmt);
while (ii == 0 || ii==MYSQL_DATA_TRUNCATED) /* fetch each row */
{
/* display row values */
printf ("%d ", my_int);
printf ("%.2f ", my_float);
printf ("%04d-%02d-%02d %02d:%02d:%02d\n",
my_datetime.year,
my_datetime.month,
my_datetime.day,
my_datetime.hour,
my_datetime.minute,
my_datetime.second);
ii=mysql_stmt_fetch (stmt);
}
mysql_stmt_free_result (stmt); /* deallocate result set */
}