Question

我从select查询得到结果，但是当我尝试增加$ slot的值然后在我的表中插入2行时，我想只添加1行，增加的插槽值。

这是我的代码

       try{
 $slot_query="Select max(slot) AS maxslot from mdl_quiz_slots where quizid=$quiid";
     $queryResult=db_query($slot_query);
     foreach ($queryResult as $row) {
 $slot=$row->maxslot;
 $slot++;
 $question_query ="INSERT INTO mdl_quiz_slots ".
   "(slot,quizid,page,requireprevious,questionid,maxmark)".
   "VALUES ".
   "('$slot','$quiid','$page','$requireprevious','$questid','$maxmark')";
    $queryResult=db_query($question_query);

    }

Answer 1

我并不认真地提倡这个解决方案，但无论如何你都可以玩这个......

CREATE TABLE my_table (i INT NOT NULL UNIQUE);

INSERT INTO my_table SELECT COALESCE(MAX(i)+1,1) FROM (SELECT 1) x, my_table LIMIT 1;

SELECT * FROM my_table;
+---+
| i |
+---+
| 1 |
+---+

INSERT INTO my_table SELECT COALESCE(MAX(i)+1,1) FROM (SELECT 1) x, my_table LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

SELECT * FROM my_table;
+---+
| i |
+---+
| 1 |
| 2 |
+---+
2 rows in set (0.00 sec)

Answer 2

我不知道这里是否有足够的信息可以解决，因为我感觉你曾经两次调用整个试用片段。

因为您正在调用select max查询，所以我只期望一个结果，但不确定您的自定义数据库包装类中发生了什么。因此，您可能会尝试将insert语句移出循环

try{
 $slot_query="Select max(slot) AS maxslot from mdl_quiz_slots where quizid=$quiid";
 $queryResult=db_query($slot_query);
 foreach ($queryResult as $row) {
   $slot=$row->maxslot;
   $slot++;
 }

$question_query ="
INSERT INTO mdl_quiz_slots 
(slot,quizid,page,requireprevious,questionid,maxmark)
VALUES
('$slot','$quiid','$page','$requireprevious','$questid','$maxmark');
";
$queryResult=db_query($question_query);

}

我想从数据库中获取一个值，然后将其递增以在插入查询中使用

2 个答案: