diff -u b/core/lib/Drupal/Core/Database/Connection.php b/core/lib/Drupal/Core/Database/Connection.php
--- b/core/lib/Drupal/Core/Database/Connection.php
+++ b/core/lib/Drupal/Core/Database/Connection.php
@@ -1176,7 +1176,7 @@
   }
 
   /**
-   * Retrieves an unique ID from a given sequence.
+   * Retrieves a unique ID from a given sequence.
    *
    * Use this function if for some reason you can't use a serial field. For
    * example, MySQL has no ways of reading of the current value of a sequence
@@ -1184,7 +1184,7 @@
    * value. Or sometimes you just need a unique integer.
    *
    * @param $existing_id
-       Maximum existing id
+   *   This must be a Maximum existing ID.
    *   After a database import, it might be that the sequences table is behind,
    *   so by passing in the maximum existing id, it can be assured that we
    *   never issue the same id.
diff -u b/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php b/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
--- b/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Connection.php
@@ -147,7 +147,6 @@
     $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} Engine=MEMORY ' . $query, $args, $options);
     return $tablename;
   }
-
   /**
    * {@inheritdoc}
    */
diff -u b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
--- b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/mysql/Schema.php
@@ -35,15 +35,11 @@
   /**
    * Get information about the table name and database 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's
+   * default key for prefix.
    * @param bool $add_prefix
-   *
+   * Boolean that indicates whether the given table name should be prefixed.
    * @return array
    *   A keyed array with information about the database, table name and prefix.
    */
@@ -84,12 +80,11 @@
   /**
    * Generate SQL to create a new table from a Drupal schema definition.
    *
-   * @param string $name
+   * @param $name
    *   The name of the table to create.
-   * @param array $table
+   * @param $table
    *   A Schema API table definition array.
-   *
-   * @return string[]
+   * @return
    *   An array of SQL statements to create the table.
    */
   protected function createTableSql($name, $table) {
@@ -146,7 +141,7 @@
    *   The field specification, as per the schema data structure format.
    *
    * @return string
-   *   The Generated SQL string.
+   *   The generated SQL string.
    */
   protected function createFieldSql($name, $spec) {
     $sql = "`" . $name . "` " . $spec['mysql_type'];
diff -u b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
--- b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Connection.php
@@ -22,7 +22,7 @@
 class Connection extends DatabaseConnection {
 
   /**
-   * The name by which to obtain a lock for retrieve the next insert ID.
+   * The name used to obtain a lock to retrieve the next insert ID.
    */
   const POSTGRESQL_NEXTID_LOCK = 1000;
 
@@ -185,7 +185,6 @@
     $this->query('CREATE TEMPORARY TABLE {' . $tablename . '} AS ' . $query, $args, $options);
     return $tablename;
   }
-
   /**
    * {@inheritdoc}
    */
@@ -253,7 +252,8 @@
    * @return
    *   An integer number larger than any number returned by earlier calls and
    *   also larger than $existing if one was passed in.
-   */
+    */
+
   public function nextId($existing = 0) {
 
     // Retrieve the name of the sequence. This information cannot be cached
diff -u b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
--- b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/pgsql/Schema.php
@@ -188,7 +188,6 @@
    *   The name of the table to create.
    * @param array $table
    *   A Schema API table definition array.
-   *
    * @return string[]
    *   An array of SQL statements to create the table.
    */
@@ -377,14 +376,13 @@
       );
     return $map;
   }
-
   /**
    * Generates SQL from field definitions.
    *
    * @param array $fields
    *   Array of field definitions. Each array value is either:
-   *   - a field name (string),
-   *   - an array of two strings, array($field_name, $alias).
+   *   - A field name (string).
+   *   - An array containing the field name and field alias.
    *
    * @return string
    *   The generated SQL snippet.
@@ -449,7 +447,9 @@
     $prefixInfo = $this->getPrefixInfo($new_name);
     $this->connection->query('ALTER TABLE {' . $table . '} RENAME TO ' . $prefixInfo['table']);
   }
-
+  /**
+  * {@inheritdoc}
+  */
   public function copyTable($source, $destination) {
     // @TODO The server is likely going to rename indexes and constraints
     //   during the copy process, and it will not match our
@@ -713,14 +713,16 @@
   }
 
   /**
+   *  Generates Index SQL from field definitions.
+   *
    * @param string $table
    *   The table on which the index will be created.
    * @param string $name
    *   An identifying name for this index.
    * @param array $fields
    *   Array of field definitions. Each array value is either
-   *   - a field name (string), or
-   *   - an array of two strings, array($field_name, $alias).
+   *   - A field name (string).
+   *   - An array containing the field name and field alias.
    *
    * @return string
    *   The generated SQL snippet.
@@ -754,6 +756,9 @@
    *   The database table to return comments for.
    * @param $column
    *   (optional) A column in $table to return comments for.
+   *
+   * @return string
+   *   The generated SQL string.
    */
   public function getComment($table, $column = NULL) {
     $info = $this->getPrefixInfo($table);
diff -u b/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php b/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
--- b/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
+++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Connection.php
@@ -16,9 +16,11 @@
 use Drupal\Core\Database\Connection as DatabaseConnection;
 
 /**
-  * SQLite implementation of DatabaseConnection::prepare(). SQLite implementation of
-  * \Drupal\Core\Database\Connection::prepare().
-  */
+ * @addtogroup database
+ * @{
+ * SQLite implementation of DatabaseConnection::prepare(). SQLite implementation of
+ * \Drupal\Core\Database\Connection::prepare().
+ */
 class Connection extends DatabaseConnection {
 
   /**
@@ -100,7 +102,6 @@
     $version = $this->query('SELECT sqlite_version()')->fetchField();
     $this->savepointSupport = (version_compare($version, '3.6.8') >= 0);
   }
-
   /**
    * {@inheritdoc}
    */
@@ -177,7 +178,8 @@
    * @param mixed $expr2
    *   (optional) Returned if $condition results to FALSE.
    *
-   * @return
+   * @return string
+   *   The generated SQL string.
    */
   public static function sqlFunctionIf($condition, $expr1, $expr2 = NULL) {
     return $condition ? $expr1 : $expr2;