有没有一种方法可以搜索mySQL数据库中的所有表？

Question

Basically I have a database full of tables and I want to go through them all until I find a result that matches my search query. Is there a way to do this? Or at least a command to return all of the table names so that I could loop through them until I find the right value?

thanks!

Answer 1

Aaah, search engines. Exciting subject, but I would rather build something with internal intelligence rather than using brute force solution. Yes - checking every table/column in database is brute force and may result in sluggishness and false positives.

Let me present you with something I would use instead. With below solution each table/column worth scanning needs to be added manually, but everything else is automatic. Here's the usage:

$e = new SearchEngine();
$e->addTable('users', 'id', 'login'); // table, primary key name, column to be searched in
$e->addTable('users', 'id', 'last_name');
$e->addTable('towns', 'id', 'name');

print_r($e->search('austin')); // we search for exact match for word "austin"

And here's how it was implemented:

class SearchEngine {

    protected $tables = array();

    public function addTable($table, $key, $column) {
        $this->tables[] = array(
            'table' => $table,
            'key' => $key,
            'column' => $column
        );
    }

    public function search($term) {
        $q = array();
        foreach ($this->tables as $t) {
            list($table, $key, $column) = $t;
            $q[] = "
                SELECT
                    $key AS searched_key,
                    '$key' AS searched_key_name,
                    '$table' AS searched_table,
                    '$column' AS searched_column,
                    $column AS searched_value
                FROM $table
                WHERE $column = $term
            ";
        }
        $sql = implode(' UNION ', $q);
        // query the database
        // return results
    }

} // class SearchEngine

Let's analyse example output:

searched_key | searched_key_name | searched_table | searched_column | searched_value
-------------+-------------------+----------------+-----------------+---------------
         276 |                id | users          | login           | austin
        1782 |                id | users          | last_name       | austin
          71 |                id | towns          | name            | austin

From the table above you can figure out that phrase "austin" was found in table users , column login (primary key 276) and column last_name (primary key 1782). It was also found in table towns in column name (primary key 71);

Such search result may be sufficient for you. Or else, you can further process the list to select full row from each table:

$out = array();
foreach ($rows as $row) {
    $sql = "
        SELECT * FROM {$row['searched_table']}
        WHERE {$row['searched_key_name']} = {$row['searched_key']}
        LIMIT 1
    ";
    // query the database
    // append result to $out array
}
return $out;

This way you will end up with full search result (as opposed to intermediate results from previous table):

id: 276, login: austin, last_name: Powers, email: austin.powers@gmail.com
id: 1782, login: michael, last_name: austin, email: michael.e@gmail.com
id: 71, name: austin, state: texas, country: usa

Because current implementation is restricted to fixed comparison operator (WHERE field = value), you may want to introduce some flexibility here. If so, search operator needs to be delegated to external class and injected into search() function:

public function search(SearchOperator $operator, $term) {
...

Then SearchOperator needs to be taken into account by replacing WHERE condition with the below:

WHERE {$operator->toSQL($column, $term)}

Now let's focus on SearchOperator implementation. Since operator implementation provides only one method, namely toSQL , we don't need full class, or even abstract class. Interface will suffice in this case:

interface SearchOperator {

    public function toSQL($column, $term);

} // interface SearchOperator

And let's define couple of implementations representing = (equals) and LIKE operators:

class Equals implements SearchOperator {

    public function toSQL($column, $term) {
        return "$column = '$term'";
    }

} // class Equals

class Like implements SearchOperator {

    public function toSQL($column, $term) {
        return "$column LIKE '$term'";
    }

} // class Like

Naturally, any other implementation is possible - think about classes called StartsWith, EndsWith, or DoesNotContain.

See updated solution usage:

$e = new SearchEngine();
$e->addTable('users', 'id', 'login');
$e->addTable('users', 'id', 'last_name');
$e->addTable('towns', 'id', 'name');

print_r($e->search(new Like(), 'austin%')); // here we search for columns being LIKE 'austin%'

Time to leave some final remarks:

• Above examples are incomplete. Database querying code was omitted for clarity.
• SQL used in examples does not sanitize input data. I strongly urge you to use prepared statements with bound parameters to avoid huge security risk.
• Search algorithm presented above is a naive one. Some optimisation can be done (ie grouping queries referring to the same table). But don't optimise prematurely - wait until it becomes a real issue.

Hoping this was helpful.

Answer 2

Very bad idea. However, should you need to search all tables (and you are using MySQL) you can get a list with:

SHOW TABLES;

And then loop through each and (assuming you know the columns) query them.

Answer 3

我猜您可以为此使用Mysql的全文搜索吗？

Answer 4

As others have said, it's possible to extract all the tables names and their column names from meta data dictionary. Take a look at the "information_schema" database. You can get a list of tables which you can then iterate over.

But chances are you are using the database wrong. We don't query the database, we query the data model. The data model is implemented as a set of tables/views etc.

Can you provide us with some background as to why you need to do this? Maybe there are better alternatives?

Answer 5

You can get all the tables in your database with

SHOW TABLES;

Then you can loop through the tables and find out the structure for each table with

DISPLAY table_name;

But you still would need to have a vague idea about how to query to columns of each table in order to find anything. So unless you have a more specialized problem, eg al tables have the same known structure, I would agree with the sentiment that you might be using the database wrong and there might be a better way.

Answer 6

ridona有一个不错的图书馆，可以读取所有表格