diff --git a/core/lib/Drupal/Core/Database/Schema.php b/core/lib/Drupal/Core/Database/Schema.php
index f064156..f2490e8 100644
--- a/core/lib/Drupal/Core/Database/Schema.php
+++ b/core/lib/Drupal/Core/Database/Schema.php
@@ -25,6 +25,8 @@
 
   /**
    * The placeholder counter.
+   *
+   * @var int
    */
   protected $placeholder = 0;
 
@@ -41,9 +43,17 @@
 
   /**
    * A unique identifier for this query object.
+   *
+   * @var string
    */
   protected $uniqueIdentifier;
 
+  /**
+   * @param \Drupal\Core\Database\Driver\Sqlite\Connection $connection
+   * SQLite object for DatabaseConnection.
+   *
+   */
+
   public function __construct($connection) {
     $this->uniqueIdentifier = uniqid('', TRUE);
     $this->connection = $connection;
@@ -51,6 +61,8 @@ public function __construct($connection) {
 
   /**
    * Implements the magic __clone function.
+   *
+   * @return string
    */
   public function __clone() {
     $this->uniqueIdentifier = uniqid('', TRUE);
@@ -65,6 +77,8 @@ public function uniqueIdentifier() {
 
   /**
    * Implements PlaceHolderInterface::nextPlaceholder().
+   *
+   * @return string
    */
   public function nextPlaceholder() {
     return $this->placeholder++;
@@ -73,13 +87,13 @@ public function nextPlaceholder() {
   /**
    * Get information about the table name and schema from the prefix.
    *
-   * @param
-   *   Name of table to look prefix up for. Defaults to 'default' because that's
-   *   default key for prefix.
-   * @param $add_prefix
-   *   Boolean that indicates whether the given table name should be prefixed.
+   * @param string $table
+   *   Name of table to look prefix up for. Defaults to 'default' because that
+   *   is the default key for prefix.
+   * @param bool $add_prefix
+   *   TRUE, if the given table name should be prefixed. FALSE, otherwise.
    *
-   * @return
+   * @return array
    *   A keyed array with information about the schema, table name and prefix.
    */
   protected function getPrefixInfo($table = 'default', $add_prefix = TRUE) {
@@ -131,17 +145,17 @@ function prefixNonTable($table) {
    * method should be overwritten by a database driver if the database provider
    * uses alternate methods. Because information_schema.tables is used in a few
    * different functions, a database driver will only need to override this function
-   * to make all the others work. For example see
+ * to make all the others work. For example see
    * core/includes/databases/mysql/schema.inc.
    *
-   * @param $table_name
+   * @param string $table_name
    *   The name of the table in question.
    * @param $operator
    *   The operator to apply on the 'table' part of the condition.
    * @param $add_prefix
    *   Boolean to indicate whether the table name needs to be prefixed.
    *
-   * @return \Drupal\Core\Database\Query\Condition
+   * @return bool \Drupal\Core\Database\Query\Condition
    *   A Condition object.
    */
   protected function buildTableNameCondition($table_name, $operator = '=', $add_prefix = TRUE) {
@@ -160,10 +174,10 @@ protected function buildTableNameCondition($table_name, $operator = '=', $add_pr
   /**
    * Check if a table exists.
    *
-   * @param $table
+   * @param string $table
    *   The name of the table in drupal (no prefixing).
    *
-   * @return
+   * @return bool
    *   TRUE if the given table exists, otherwise FALSE.
    */
   public function tableExists($table) {
@@ -183,7 +197,7 @@ public function tableExists($table) {
    * @param string $table_expression
    *   An SQL expression, for example "cache_%" (without the quotes).
    *
-   * @return array
+   * @return string[]
    *   Both the keys and the values are the matching tables.
    */
   public function findTables($table_expression) {
@@ -239,12 +253,12 @@ public function findTables($table_expression) {
   /**
    * Check if a column exists in the given table.
    *
-   * @param $table
+   * @param string $table
    *   The name of the table in drupal (no prefixing).
-   * @param $name
+   * @param string $column
    *   The name of the column.
    *
-   * @return
+   * @return bool
    *   TRUE if the given column exists, otherwise FALSE.
    */
   public function fieldExists($table, $column) {
@@ -609,10 +623,12 @@ public function createTable($name, $table) {
    * This is usually an identity function but if a key/index uses a column prefix
    * specification, this function extracts just the name.
    *
-   * @param $fields
-   *   An array of key/index column specifiers.
+   * @param array $fields
+   *   An array of key/index column specifiers. Each array value can be either
+   *   - a string field name.
+   *   - an of two strings: array($field_name, $field_alias).
    *
-   * @return
+   * @return string[]
    *   An array of field names.
    */
   public function fieldNames($fields) {
@@ -631,13 +647,13 @@ public function fieldNames($fields) {
   /**
    * Prepare a table or column comment for database query.
    *
-   * @param $comment
+   * @param string $comment
    *   The comment string to prepare.
-   * @param $length
+   * @param int $length
    *   Optional upper limit on the returned string length.
    *
-   * @return
-   *   The prepared comment.
+   * @return string|false
+   *   The prepared comment, or FALSE if the driver does not support it.
    */
   public function prepareComment($comment, $length = NULL) {
     // Remove semicolons to avoid triggering multi-statement check.
diff --git a/core/lib/Drupal/Core/Database/Statement.php b/core/lib/Drupal/Core/Database/Statement.php
index 1625bab..671e89f 100644
--- a/core/lib/Drupal/Core/Database/Statement.php
+++ b/core/lib/Drupal/Core/Database/Statement.php
@@ -36,6 +36,11 @@ class Statement extends \PDOStatement implements StatementInterface {
    */
   public $allowRowCount = FALSE;
 
+  /**
+   * @param \Drupal\Core\Database\Connection $dbh
+   * Connection object to perform database queries.
+   */
+
   protected function __construct(Connection $dbh) {
     $this->dbh = $dbh;
     $this->setFetchMode(\PDO::FETCH_OBJ);
diff --git a/core/lib/Drupal/Core/Database/StatementInterface.php b/core/lib/Drupal/Core/Database/StatementInterface.php
index 6792e3e..970612a 100644
--- a/core/lib/Drupal/Core/Database/StatementInterface.php
+++ b/core/lib/Drupal/Core/Database/StatementInterface.php
@@ -47,13 +47,13 @@
   /**
    * Executes a prepared statement
    *
-   * @param $args
+   * @param array $args
    *   An array of values with as many elements as there are bound parameters in
    *   the SQL statement being executed.
-   * @param $options
+   * @param array $options
    *   An array of options for this query.
    *
-   * @return
+   * @return bool
    *   TRUE on success, or FALSE on failure.
    */
   public function execute($args = array(), $options = array());
@@ -61,7 +61,7 @@ public function execute($args = array(), $options = array());
   /**
    * Gets the query string of this statement.
    *
-   * @return
+   * @return string
    *   The query string, in its form with placeholders.
    */
   public function getQueryString();
@@ -84,16 +84,18 @@ public function rowCount();
    * See http://php.net/manual/pdo.constants.php for the definition of the
    * constants used.
    *
-   * @param $mode
+   * @param int $mode
    *   One of the PDO::FETCH_* constants.
-   * @param $a1
+   * @param int|string|object $a1
    *   An option depending of the fetch mode specified by $mode:
    *   - for PDO::FETCH_COLUMN, the index of the column to fetch
    *   - for PDO::FETCH_CLASS, the name of the class to create
    *   - for PDO::FETCH_INTO, the object to add the data to
-   * @param $a2
+   * @param array $a2
    *   If $mode is PDO::FETCH_CLASS, the optional arguments to pass to the
    *   constructor.
+   *
+   * @see \PDOStatement::setFetchMode()
    */
    public function setFetchMode($mode, $a1 = NULL, $a2 = array());
 
@@ -111,19 +113,22 @@ public function setFetchMode($mode, $a1 = NULL, $a2 = array());
    * @param $cursor_offset
    *   Not implemented in all database drivers, don't use.
    *
-   * @return
+   * @return mixed
    *   A result, formatted according to $mode.
    */
    public function fetch($mode = NULL, $cursor_orientation = NULL, $cursor_offset = NULL);
 
-  /**
-   * Returns a single field from the next record of a result set.
+   /**
+   * Returns a single field value from the next row of a result set.
    *
-   * @param $index
-   *   The numeric index of the field to return. Defaults to the first field.
+   * Mimicks the \PDO::fetchColumn() method.
+   * @link http://php.net/manual/en/pdostatement.fetchcolumn.php
    *
-   * @return
-   *   A single field from the next record, or FALSE if there is no next record.
+   * @param int $index
+   *   The column index.
+   *
+   * @return string|false
+   *   The fetched field value, or FALSE, if no further row was found.
    */
   public function fetchField($index = 0);
 
@@ -150,14 +155,14 @@ public function fetchAssoc();
   /**
    * Returns an array containing all of the result set rows.
    *
-   * @param $mode
+   * @param int $mode
    *   One of the PDO::FETCH_* constants.
-   * @param $column_index
+   * @param int $column_index
    *   If $mode is PDO::FETCH_COLUMN, the index of the column to fetch.
-   * @param $constructor_arguments
+   * @param array $constructor_arguments
    *   If $mode is PDO::FETCH_CLASS, the arguments to pass to the constructor.
    *
-   * @return
+   * @return array[]|object[]|mixed[]
    *   An array of results.
    */
    function fetchAll($mode = NULL, $column_index = NULL, $constructor_arguments = NULL);
@@ -167,10 +172,10 @@ function fetchAll($mode = NULL, $column_index = NULL, $constructor_arguments = N
    *
    * Note that this method will run the result set to the end.
    *
-   * @param $index
+   * @param int $index
    *   The index of the column number to fetch.
    *
-   * @return
+   * @return mixed[]
    *   An indexed array, or an empty array if there is no result set.
    */
   public function fetchCol($index = 0);
@@ -185,12 +190,12 @@ public function fetchCol($index = 0);
    *
    * Note that this method will run the result set to the end.
    *
-   * @param $key_index
+   * @param int $key_index
    *   The numeric index of the field to use as the array key.
-   * @param $value_index
+   * @param int $value_index
    *   The numeric index of the field to use as the array value.
    *
-   * @return
+   * @return mixed[]
    *   An associative array, or an empty array if there is no result set.
    */
   public function fetchAllKeyed($key_index = 0, $value_index = 1);
@@ -201,15 +206,15 @@ public function fetchAllKeyed($key_index = 0, $value_index = 1);
    * If the given key appears multiple times, later records will overwrite
    * earlier ones.
    *
-   * @param $key
+   * @param int $key
    *   The name of the field on which to index the array.
-   * @param $fetch
+   * @param int $fetch
    *   The fetchmode to use. If set to PDO::FETCH_ASSOC, PDO::FETCH_NUM, or
    *   PDO::FETCH_BOTH the returned value with be an array of arrays. For any
    *   other value it will be an array of objects. By default, the fetch mode
    *   set for the query will be used.
    *
-   * @return
+   * @return array[]|object[]
    *   An associative array, or an empty array if there is no result set.
    */
   public function fetchAllAssoc($key, $fetch = NULL);
diff --git a/core/lib/Drupal/Core/Database/StatementPrefetch.php b/core/lib/Drupal/Core/Database/StatementPrefetch.php
index 0fbfc04..7ef01b5 100644
--- a/core/lib/Drupal/Core/Database/StatementPrefetch.php
+++ b/core/lib/Drupal/Core/Database/StatementPrefetch.php
@@ -131,6 +131,20 @@ class StatementPrefetch implements \Iterator, StatementInterface {
    */
   public $allowRowCount = FALSE;
 
+  /**
+   * @param \PDO $dbh
+   * Php Database object.
+   *
+   * @param \Drupal\Core\Database\Connection $connection
+   * Connection object to perform Database operations.
+   *
+   * @param string $query
+   * Query string to fetch data.
+   *
+   * @param array $driver_options
+   * Connection Driver specific options.
+   */
+
   public function __construct(\PDO $pdo_connection, Connection $connection, $query, array $driver_options = array()) {
     $this->pdoConnection = $pdo_connection;
     $this->dbh = $connection;
@@ -217,8 +231,8 @@ protected function throwPDOException() {
    * Some drivers (including SQLite) will need to perform some preparation
    * themselves to get the statement right.
    *
-   * @param $query
-   *   The query.
+   * @param string $query
+   *   The query string.
    * @param array $args
    *   An array of arguments.
    * @return \PDOStatement
@@ -267,7 +281,7 @@ public function setFetchMode($mode, $a1 = NULL, $a2 = array()) {
    * array position in $this->data and format it according to $this->fetchStyle
    * and $this->fetchMode.
    *
-   * @return mixed
+   * @return array|mixed|object
    *   The current row formatted as requested.
    */
   public function current() {