CODEWITHSUNDEEP
phpdatabasesyntax
Petru Lebada
Petru Lebada

Reputation: 1682

Why this syntax works?

I tried to list all of my databases so I have used this:

$sql="SHOW DATABASES"; 
    $query=mysql_query($sql,$connect);

then I fetch the db into an array, and I also listed the tables of each db from this array:

 while ($row = mysql_fetch_assoc($query)){
$sql3="SHOW TABLES FROM `".$row['Database']."`"; //**i dont understand why $row['Database'] works?**
$query3=mysql_query($sql3, $connect);
}

Let's give an example array(db1,db2,db3). When I use: 

SHOW TABLES FROM `".$row['Database'].

it will show each table from: 

$row[0](db1) , $row[1](db2) , $row[2](db3)

Am I right? This is the theory behind this syntax? Or what?

Upvotes: 1

Views: 60

Answers (2)

Sal00m
Sal00m

Reputation: 2916

You are accessing the array result by index name, if you make a print_r of the variable $row you will get something like this:

Array
(
    [Database] => information_schema
)
Array
(
    [Database] => mysql
)

So you can access the value by using Database index

EDITED:

In case of tables you will get something like this:

Array
(
    [Tables_in_information_schema] => CHARACTER_SETS
)
...
Array
(
    [Tables_in_mysql] => columns_priv
)

So the the index will change with every table, you can access it with something like this:

while ($row2 = mysql_fetch_assoc($query3)){
    echo $row2["Tables_in_{$row['Database']}"];
}

OR

You can use mysql_fetch_row instead, an access it using position:

while ($row2 = mysql_fetch_row($query3)){
    echo $row2[0];
}

IMPORTANT:

I forgot to mention, but mysql_ extension is deprecated so you should use PDO or mysqli_ functions instead

Upvotes: 3

Jens Schauder
Jens Schauder

Reputation: 81988

I don't know the language you are using. But database queries typically return a resultsets, that allow you do access the values from different columns either by the index of the column or by it's name. The later is what you are doing here.

Upvotes: 0

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