Dynamic select query in mysql? - php

Question

I am using mysql as my database and php as server side language.
As we know that we can select data from database using select query.
Below example is important!!
select * from table
select name from table
select name,salary from table where salary > 10000
etc..........
now, for different select query of a table we need different select method. because every time select * is not good because it takes a huge time.
Now, My Question is how write dynamic single get method of a single table by which we can achieve our requirement (shown in example...)?
I will pass the array of parameters in the argument of the function.. for ex. in php
public get($arr)
{
//code goes here
}
I want to fetch the $arr and want to change the sql dynamically..
Don't want any join query just simple select as shown in above..

Answer 1

Depending on how you want to do it, you can do something like this:
public get($arrfield, $arrtable, $arrwhere)
{
$str = "SELECT " . $arrfield . " FROM " . $arrtable . " WHERE " . $arrwhere;
return $str;
// You can return the query string or run the query and return the results
}

Answer 2

Trust me, to write all three queries is not that too hard a job that have to be avoided at any cost.
Please, do not obfuscate a precious SQL language into unreadable gibberish. Not to mention innumerable security breaches of your approach.
What you should think of is a function that lets you to use parameters. Thus, better make our function like this
function mysqli($mysqli, $query, $params, $types = NULL)
{
$statement = $mysqli->prepare($select);
$types = $types ?: str_repeat('s', count($params));
$statement->bind_param($types, ...$params);
$statement->execute();
return $statement;
}
and run your every query as is, only providing placeholders instead of variables
select * from table:
you'll never need a query like this
select name from table
$names = mysqli($db, "select name from table")->get_result->fetch_all();
`select name,salary from table:
$stmt = mysqli($db, "select name from table where salary > ?", [10000]);
$names = $stmt->get_result->fetch_all();
See - the query itself is the least code portion. Your concern should be not SQL but useless reprtitive parts of PHP code used to run a query and to fetch the data.

Answer 3

Here is the structure of the dynamic query.Please add required validation.You can add 'Or' clause also.On the basis of parameter or data type you can do it. Like
public SelectTable($arrfield, $table, $arrwhere, $arrgroup)
{
if(!empty($arrfield))
{
$fields = implode('`,`',$arrfield);
}
else
{
$fields = '*';
}
if(!empty($arrwhere))
{
foreach($arrwhere as $fieldName=>$fieldValue)
{
if(is_array($fieldValue))
{
$cond .= "`fieldName` in (". implode(',',$fieldValue) );
}
else
$cond .= "`fieldName` = '" . addslashes($fieldValue)."'";
}
}
else
{
$cond = '1';
}
if(!empty($arrgroup))
{
$groupBy .= " group by ";
foreach($arrgroup as $field=>$value)
{
$groupBy .= $field . " " . $vale;
}
}
}
$str = "SELECT " . $fields . " FROM " . $table . " WHERE " . $cond . $groupBy;
return $str;
// You can return the query string or run the query and return the results
}