存儲過程中的准備好的語句不起作用

Question

我試圖在存儲過程中執行准備好的語句。

但是我遇到了問題。

這是存儲過程：

DELIMITER $$
CREATE DEFINER=`root`@`localhost` PROCEDURE `getAllUserLunchReport`(IN `start_date` DATETIME, IN `end_date` DATETIME)
BEGIN

SET GLOBAL group_concat_max_len=4294967295;
SET @SQL = NULL;
SET @start_date = DATE(start_date);
SET @end_date = DATE(end_date);

    SELECT
    GROUP_CONCAT(DISTINCT
        CONCAT(
        'SUM(CASE WHEN date = "',DATE(issuedDateTime),'" THEN lunchStatus ELSE 0 END) AS `',DATE(issuedDateTime),'`'
        )
    ) INTO @SQL

        FROM `lunch_status` 
        WHERE DATE(issuedDateTime) BETWEEN @start_date AND @end_date;

    SET @SQL 
    = CONCAT('SELECT userId, ', @SQL, ' 
    FROM
    (
        SELECT userId, lunchStatus, DATE(issuedDateTime) as date 
        FROM `lunch_status` 
        WHERE DATE(issuedDateTime) BETWEEN "',@start_date,'" AND "',@end_date,'" 
    ) as a
    GROUP BY userId;');

PREPARE stmt FROM @SQL;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

END$$
DELIMITER ;

這是錯誤：

PDOStatement: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'NULL' at line 1

這是控制器：

public function weeklyLunchReport($date1=null, $date2=null)
{
    $user = AclHelper::getCurrentUser();
    $default_userID = intval($user['user_id']);
    $defDate = new DateTime();
    $default_date = $defDate->format('Y-m-d');

    $date1 = (isset($date1) && $date1 != '') ? $date1 : $default_date;
    $date2 = (isset($date2) && $date2 != '') ? $date2 : $default_date;

    $records = $this->db->exec("CALL getAllUserLunchReport ('$date1','$date2')");
    return $records;
}

還：這是SQL變量的值：

SELECT userId, 
SUM(CASE WHEN date = "2018-06-03" THEN lunchStatus ELSE 0 END) AS `2018-06-03`,
SUM(CASE WHEN date = "2018-06-04" THEN lunchStatus ELSE 0 END) AS `2018-06-04`,
SUM(CASE WHEN date = "2018-06-06" THEN lunchStatus ELSE 0 END) AS `2018-06-06`,
SUM(CASE WHEN date = "2018-06-07" THEN lunchStatus ELSE 0 END) AS `2018-06-07`,
SUM(CASE WHEN date = "2018-06-08" THEN lunchStatus ELSE 0 END) AS `2018-06-08` 
   FROM
   (
       SELECT userId, lunchStatus, DATE(issuedDateTime) as date 
       FROM `lunch_status` 
       WHERE DATE(issuedDateTime) BETWEEN "2018-06-03" AND "2018-06-09" 
   ) as a
   GROUP BY userId;

單獨運行此查詢字符串將提供預期的結果集。

該查詢似乎很好，但是我不知道它哪里出錯了。

很感謝任何形式的幫助。 提前致謝。

Answer 1

我在mysql客戶端中嘗試了您的過程，因此要排除任何與PHP相關的問題：

mysql> create table lunch_status (userId int, lunchstatus int, issueddatetime datetime);

mysql> DELIMITER $$
mysql> CREATE DEFINER=`root`@`localhost` PROCEDURE `getAllUserLunchReport`(IN `start_date` DATETIME, IN `end_date` DATETIME)
    -> BEGIN ...

mysql> CALL getAllUserLunchReport ('2018-06-17','2018-06-17');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NULL' at line 1
mysql> select @SQL;
+------+
| @SQL |
+------+
| NULL |
+------+

但是，當我嘗試插入日期范圍內的行時：

mysql> insert into lunch_status values (123, 1, now());
Query OK, 1 row affected (0.02 sec)

mysql> CALL getAllUserLunchReport ('2018-06-17','2018-06-17');
+--------+------------+
| userId | 2018-06-17 |
+--------+------------+
|    123 |          1 |
+--------+------------+

問題在於，當您要搜索的日期范圍內沒有行時， GROUP_CONCAT()為數據透視表列列表生成NULL。

然后，您將NULL的CONCAT（）放入完整的SELECT語句中，但是CONCAT('SELECT ...', NULL, 'FROM ...')產生NULL，因為將任何字符串與NULL串聯都會產生NULL。

您需要確保GROUP_CONCAT()默認為一些非NULL字符串：

SELECT
    COALESCE(GROUP_CONCAT(DISTINCT
        CONCAT(
        'SUM(CASE WHEN date = "',DATE(issuedDateTime),'" THEN lunchStatus ELSE 0 END) AS `',DATE(issuedDateTime),'`'
        )
    ), '0 as `NoMatchingRows`') INTO @SQL

調用該過程仍將不返回任何結果集，因為表中沒有與您指定的日期范圍匹配的日期。 但是，當您嘗試准備NULL時，至少不會出現語法錯誤。