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1. Please write a function to achieve the following functions:
Convert the string "open_door" into "OpenDoor", "make_by_id" is converted to "MakeById".
function str_change($str) {
$str = str_replace ( "_", " ", $str );
$str = ucwords ( $str );
$str = str_replace ( " ", "", $str );
return $str; }
2. It is required to write a program to convert the following array $arr1 into array $arr2:
$arr1 = array (
'0' => array ('fid' => 1, 'tid ' => 1, 'name' =>'Name1' ),
'1' => array ('fid' => 1, 'ti' => 2, 'name' => 'Name2' ),
'2' => array ('fid' => 1, 'tid' => 5, 'name' =>'Name3'),
'3' = > array ('fid' => 1, 'tid' => 7, 'name' =>'Name4'),
'4' => array ('fid' => 3, 'tid' => 9, 'name' =>'Name5')
);
$arr2 = array (
'0' => array (
'0' => ; array ( 'tid' => 1, 'name' => 'Name1'),
'1' => array ( 'tid' => 2, 'name' => 'Name2' ),
'2' => array ( 'tid' => 5, 'name' => 'Name3'),
'3' => array ( 'tid' => 7 , 'name' => 'Name4') ),
'1' => array (
'0' => array ( 'tid' => 9, 'name' => ' Name5′ ) ) );
$arr1 = array (
'0' => array ('fid' => 1, 'tid' => , 'name' =>'Name1' ),
'1' => array ('fid' => 1, 'tid' => 2 , 'name' =>'Name2'),
'2' => array ('fid' => 1, 'tid' => 5 , 'name' =>'Name3'),
'3' => array ('fid' => 1, 'tid' => 7 , 'name' =>'Name4'),
'4' => array ('fid' => 3, 'tid' => 9 , 'name' =>' Name5')
);
function changeArrayStyle($arr){
foreach($arr as $key=>$value){
$result[$value[fid]][]= $value;
}
return array_values($result);
}
$arr2=changeArrayStyle($arr1);
echo "
";
var_dump($ arr2);
?>3. Please briefly describe the paradigm and application of database design.
Generally, the 3rd normal form is sufficient for optimizing the table structure. This can not only avoid the application being too complex, but also avoid the inefficiency of the system caused by too large SQL statements.
ANSWER:
First normal form: If each attribute of the relational pattern R cannot be decomposed, it belongs to the first normal form.
Second normal form: If R belongs to the first normal form and all non-code attributes are completely functionally dependent on the code attributes, it is in the second normal form.
Third normal form: If R belongs to the second normal form, and none of the non-code attributes is a transfer function that depends on the candidate code, then it belongs to the third normal form.