在MySQL中模拟DELETE CASCADE?
可以使数据库的副本,并把触发器在after delete
DELIMITER $$
CREATE TRIGGER ad_table1_each AFTER DELETE ON table1 FOR EACH ROW
BEGIN
INSERT INTO log VALUES (null /*autoinc id*/
, 'table1' /*tablename*/
, old.id /*tableid*/
, concat_ws(',',old.field1,old.field2 /*CSV's of fields*/
, NOW() /*timestamp*/
, 'delete'); /*what action*/
REPLACE INTO restore_table1 VALUES (old.id,
, old.field1
, old.field2
, ...);
END $$
DELIMITER ;
日志表仅仅是一个具有以下字段的表:
id integer autoincrement primary key
tablename varchar(45)
table_id integer
fields varchar(6000)
delete_time timestamp
action enum('insert','update','delete')
如果你之前做了SELECT @last_id:= max(id) FROM log
副本上的删除级联。
然后,您可以执行SELECT * FROM log WHERE id > @last_id
并获取将在级联中删除的所有行。
之后,您可以使用restore_table1重新创建复制数据库中级联中已删除的行。
我认为您可以将Johan的触发解决方案与您回滚的交易结合使用。这样可以避免需要第二个数据库以及手动还原已删除的条目。
- 添加触发器和日志表
- 每个试图删除启动事务,并删除条目
- 呈现来自日志的信息,您的用户批准
- 如果用户同意提交交易,否则回滚
唯一的问题是,如果你记录的引擎进入也支持事务处理,日志记录也会被回滚,所以你需要使用非事务引擎进行日志记录,比如MyISAM。 – Johan 2011-09-26 17:38:43
交易想法很好。事实上,我不会使用触发器,也不会使用日志。我只是模拟删除和事后回滚。 – user694971 2011-09-26 18:18:19
@ user694971:我认为如果你想向用户显示删除的条目,你需要日志。没有它,你只能显示剩余的条目,除非你的应用程序逻辑可以解决这个问题。 – Stefan 2011-09-28 15:25:50
我写了一个非常快速的黑客,完全符合你在PHP中所需要的,因为我想做的完全一样的事情,并没有找到任何资源的在线。
对你来说可能已经太迟了,但它可能对别人有帮助。
function get_referencing_foreign_keys ($database, $table) {
$query = 'SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, REFERENCED_COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE WHERE REFERENCED_TABLE_SCHEMA = "'.$database.'" AND REFERENCED_TABLE_NAME = '.esc($table);
$result = rquery($query);
$foreign_keys = array();
while ($row = mysql_fetch_row($result)) {
$foreign_keys[] = array('database' => $row[0], 'table' => $row[1], 'column' => $row[2], 'reference_column' => $row[3]);
}
return $foreign_keys;
}
function get_foreign_key_deleted_data_html ($database, $table, $where) {
$data = get_foreign_key_deleted_data ($database, $table, $where);
$html = '';
foreach ($data as $key => $this_data) {
$html .= "<h2>$key</h2>\n";
$html .= "<table>\n";
$i = 0;
foreach ($this_data as $value) {
if($i == 0) {
$html .= "\t<tr>\n";
foreach ($value as $column => $column_value) {
$html .= "\t\t<th>".htmlentities($column)."</th>\n";
}
$html .= "\t</tr>\n";
}
$html .= "\t<tr>\n";
foreach ($value as $column => $column_value) {
$html .= "\t\t<td>".htmlentities($column_value)."</td>\n";
}
$html .= "\t</tr>\n";
$i++;
}
$html .= "</table>\n";
}
return $html;
}
function get_foreign_key_deleted_data ($database, $table, $where) {
$GLOBALS['get_data_that_would_be_deleted'] = array();
$data = get_data_that_would_be_deleted($database, $table, $where);
$GLOBALS['get_data_that_would_be_deleted'] = array();
return $data;
}
function get_data_that_would_be_deleted ($database, $table, $where, $recursion = 100) {
if($recursion <= 0) {
die("Deep recursion!");
}
if($recursion == 100) {
$GLOBALS['get_data_that_would_be_deleted'] = array();
}
if($table) {
if(is_array($where)) {
$foreign_keys = get_referencing_foreign_keys($database, $table);
$data = array();
$query = 'SELECT * FROM `'.$table.'`';
if(count($where)) {
$query .= ' WHERE 1';
foreach ($where as $name => $value) {
$query .= " AND `$name` = ".esc($value);
}
}
$result = rquery($query);
$to_check = array();
while ($row = mysql_fetch_row($result)) {
$new_row = array();
$i = 0;
foreach ($row as $this_row) {
$field_info = mysql_fetch_field($result, $i);
$new_row[$field_info->name] = $this_row;
foreach ($foreign_keys as $this_foreign_key) {
if($this_foreign_key['reference_column'] == $field_info->name) {
$to_check[] = array('value' => $this_row, 'foreign_key' => array('table' => $this_foreign_key['table'], 'column' => $this_foreign_key['column'], 'database' => $this_foreign_key['database']));
}
}
$i++;
}
$GLOBALS['get_data_that_would_be_deleted'][$table][] = $new_row;
}
foreach ($to_check as $this_to_check) {
if(isset($this_to_check['value']) && !is_null($this_to_check['value'])) {
get_data_that_would_be_deleted($database, $this_to_check['foreign_key']['table'], array($this_to_check['foreign_key']['column'] => $this_to_check['value']), $recursion - 1);;
}
}
$data = $GLOBALS['get_data_that_would_be_deleted'];
return $data;
} else {
die("\$where needs to be an array with column_name => value pairs");
}
} else {
die("\$table was not defined!");
}
}
想象我有一个数据库中的“DB”被称为“表”的表,我想删除一个id为180的话,我会打电话:
print(get_foreign_key_deleted_data_html('db', 'table', array('id' => 180)));
和它打印一个包含所有行和所有将被删除的值的完整表。
但正如我所说,这是一个非常,非常快速和肮脏的黑客攻击。我会很高兴为任何错误报告(并且肯定有很多它们!)。
好问题,我也对答案感兴趣。 – Alp 2011-05-17 10:12:35
我现在能想到的唯一合理的方法是'SHOW FULL COLUMNS FROM'然后遍历相应的表...(硬编码fkey_names => table_names ...) –
user694971
2011-05-20 14:53:53