src/Database/Query/Select.php

@@ -12,6 +12,8 @@ class Select
 
     const CONDITION_HAVING = 1;
 
+    const DERIVED_TABLE_KEY = 'DERIVED';
+
     private IConnection $connection;
 
     private string $table;
@@ -55,6 +57,11 @@ class Select
         return $this;
     }
 
+    public function setDerivedTableAlias(string $tableAlias): Select
+    {
+        return $this->setTableAliases([Select::DERIVED_TABLE_KEY => $tableAlias]);
+    }
+
     public function from(string $table): Select
     {
         $this->table = $table;
@@ -194,6 +201,11 @@ class Select
         }
     }
 
+    private function isDerivedTable(): bool
+    {
+        return array_key_exists(Select::DERIVED_TABLE_KEY, $this->tableAliases);
+    }
+
     private function addJoin(string $type, $table, $column1, string $relation, $column2): void
     {
         $this->joins[] = [$type, $table, $column1, $relation, $column2];
@@ -211,10 +223,14 @@ class Select
 
     private function generateQuery(): array
     {
-        $queryString = 'SELECT ' . $this->generateColumns() . ' FROM ' . $this->generateTable($this->table, true);
+        list($innerQuery, $innerParams) = $this->generateTable($this->table, true);
+        $queryString = 'SELECT ' . $this->generateColumns() . ' FROM ' . $innerQuery;
 
         if (count($this->joins) > 0) {
-            $queryString .= ' ' . $this->generateJoins();
+            list($joinQuery, $joinParams) = $this->generateJoins();
+            $queryString .= ' ' . $joinQuery;
+        } else {
+            $joinParams = [];
         }
 
         if (count($this->conditions[self::CONDITION_WHERE]) > 0) {
@@ -245,20 +261,32 @@ class Select
             $queryString .= ' LIMIT ' . $this->limit[1] . ', ' . $this->limit[0];
         }
 
-        return [$queryString, array_merge($whereParams, $havingParams)];
+        if($this->isDerivedTable()) {
+            $queryString = '(' . $queryString . ') AS ' . $this->tableAliases[Select::DERIVED_TABLE_KEY];
         }
 
-    private function generateTable($table, bool $defineAlias = false): string
+        return [$queryString, array_merge($innerParams, $joinParams, $whereParams, $havingParams)];
+    }
+
+    private function generateTable($table, bool $defineAlias = false): array
     {
+        $params = [];
+
         if ($table instanceof RawExpression) {
-            return (string) $table;
+            return [(string) $table, $params];
+        }
+
+        if($table instanceof Select)
+        {
+            return $table->generateQuery();
         }
 
         if (isset($this->tableAliases[$table])) {
-            return ($defineAlias ? Utils::backtick($this->tableAliases[$table]) . ' ' . Utils::backtick($table) : Utils::backtick($table));
+            $queryString = ($defineAlias ? Utils::backtick($this->tableAliases[$table]) . ' ' . Utils::backtick($table) : Utils::backtick($table));
+            return [$queryString, $params];
         }
 
-        return Utils::backtick($table);
+        return [Utils::backtick($table), $params];
     }
 
     private function generateColumn($column): string
@@ -271,7 +299,8 @@ class Select
             $out = '';
 
             if ($column[0]) {
-                $out .= $this->generateTable($column[0]) . '.';
+                list($tableName, $params) = $this->generateTable($column[0]);
+                $out .= $tableName . '.';
             }
 
             $out .= Utils::backtick($column[1]);
@@ -297,15 +326,20 @@ class Select
         return implode(',', $columns);
     }
 
-    private function generateJoins(): string
+    private function generateJoins(): array
     {
         $joins = $this->joins;
         
-        array_walk($joins, function (&$value, $key) {
+        $joinQueries = [];
-            $value = $value[0] . ' JOIN ' . $this->generateTable($value[1], true) . ' ON ' . $this->generateColumn($value[2]) . ' ' . $value[3] . ' ' . $this->generateColumn($value[4]);
+        $params = [];
-        });
 
-        return implode(' ', $joins);
+        foreach($joins as $value) {
+            list($joinQueryFragment, $paramsFragment) = $this->generateTable($value[1], true);
+            array_push($joinQueries, $value[0] . ' JOIN ' . $joinQueryFragment . ' ON ' . $this->generateColumn($value[2]) . ' ' . $value[3] . ' ' . $this->generateColumn($value[4]));
+            $params = array_merge($params, $paramsFragment);
+        }
+
+        return [implode(' ', $joinQueries), $params];
     }
 
     private function generateConditions(int $type): array