如何使用动态创建的查询搜索数据库？

Question

I would like to start from an example: you received some list with needed fields. This list may vary and even if it is empty, select all fields. This list can include fields from several tables. Is there any way to generate SELECT query for doing this?

Probably there is a way, but it will look like parsing received list, adding appropriate table alias, and then adding modified list into select clause. Is it best way actually?

Update 1

• The goal is only to get passed fields from several tables, not to control result from any of them(its about first answer)

Answer 1

You could create a query that first selects dynamically fields, depending on your criteria.

for example lets assume you have two criteria passed to you. Then (after you have made sure your criteria1 and criteria2 are safe):

$mySelect = '';      //placeholder so that you can add select fields
$extraTables = '';   //placeholder to put the extra tables I may need
$criteria = " WHERE 1 ";    //this will select everything
if ($criteria1>'') {
  $mySelect .= ' , t3.field3 '; 
  $extraTables = " , aDifferentTable AS t3";
  $criteria .= " AND t3.someKey = t1.someKey '";
  $criteria .= " AND field_crit1 = '" . $criteria1 . "'";
}

//and an example of connecting dynamically to an other table
if ($criteria2>'') {
  $mySelect .= ' , t2.field5 '; 
  $extraTables = " , anOtherTable AS t2";
  $criteria .= " AND t2.someKey = t1.someKey '";
  $criteria .= " AND t2.field_crit2 = '" . $criteria2 . "'";
}

//lets combine all together into one dynamically created query    
$myquery = "SELECT t1.something " . $mySelect . " FROM myTable  AS t1";   

$myquery = $myqury . $extraTables . $criteria;