Add identifier quoting to table aliases.

Postgres & SQLServer get upset when you alias tables to User. This is
going to be pretty common so we should quote table aliases.

Cake/Database/Query.php

@@ -511,10 +511,11 @@ public function from($tables = [], $overwrite = false) {
 	protected function _buildFromPart($parts, $generator) {
 		$select = ' FROM %s';
 		$normalized = [];
+		$driver = $this->connection()->driver();
 		$parts = $this->_stringifyExpressions($parts, $generator);
 		foreach ($parts as $k => $p) {
 			if (!is_numeric($k)) {
-				$p = $p . ' ' . $k;
+				$p = $p . ' AS ' . $driver->quoteIdentifier($k);
 			}
 			$normalized[] = $p;
 		}

Cake/Test/TestCase/Database/QueryTest.php

@@ -95,7 +95,7 @@ public function testSelectFieldsFromTable() {
 		$this->assertEquals(array('body' => 'Second Article Body', 'author_id' => 3, 'name' => 'nate'), $result->fetch('assoc'));
 		$this->assertEquals(array('body' => 'Third Article Body', 'author_id' => 1, 'name' => 'nate'), $result->fetch('assoc'));
 
-		//Overwrite tables and only fetch from authors
+		// Overwrite tables and only fetch from authors
 		$result = $query->select('name', true)->from('authors', true)->order(['name' => 'desc'], true)->execute();
 		$this->assertEquals(array('nate'), $result->fetch());
 		$this->assertEquals(array('mariano'), $result->fetch());
@@ -133,6 +133,20 @@ public function testSelectAliasedFieldsFromTable() {
 		$this->assertEquals(array('text' => 'Second Article Body', 'two' => 2, 'three' => 5), $result->fetch('assoc'));
 	}
 
+/**
+ * Test that table aliases are quoted.
+ *
+ * @return void
+ */
+	public function testSelectAliasTablesAreQuoted() {
+		$query = new Query($this->connection);
+		$query = $query->select(['text' => 'a.body', 'a.author_id'])
+			->from(['a' => 'articles']);
+
+		$sql = $query->sql();
+		$this->assertRegExp('/articles AS [`"]a[`"]/', $sql);
+	}
+
 /**
  * Tests that tables can also be aliased and referenced in the select clause using such alias
  *
@@ -142,6 +156,7 @@ public function testSelectAliasedTables() {
 		$query = new Query($this->connection);
 		$result = $query->select(['text' => 'a.body', 'a.author_id'])
 			->from(['a' => 'articles'])->execute();
+
 		$this->assertEquals(['text' => 'First Article Body', 'author_id' => 1], $result->fetch('assoc'));
 		$this->assertEquals(['text' => 'Second Article Body', 'author_id' => 3], $result->fetch('assoc'));