db layer phpdoc fixes

framework/db/ActiveRecord.php

@@ -291,15 +291,15 @@ class ActiveRecord extends BaseActiveRecord
      */
     public static function getTableSchema()
     {
-        $schema = static::getDb()
+        $tableSchema = static::getDb()
             ->getSchema()
             ->getTableSchema(static::tableName());
 
-        if ($schema === null) {
+        if ($tableSchema === null) {
             throw new InvalidConfigException('The table does not exist: ' . static::tableName());
         }
 
-        return $schema;
+        return $tableSchema;
     }
 
     /**

framework/db/ColumnSchemaBuilder.php

@@ -48,6 +48,7 @@ class ColumnSchemaBuilder extends Object
     protected $default;
     /**
      * @var boolean whether the column values should be unsigned. If this is `true`, an `UNSIGNED` keyword will be added.
+     * @since 2.0.7
      */
     protected $isUnsigned = false;
 
@@ -123,6 +124,7 @@ class ColumnSchemaBuilder extends Object
      * Specify the default SQL expression for the column.
      * @param string $default the default value expression.
      * @return $this
+     * @since 2.0.7
      */
     public function defaultExpression($default)
     {
@@ -223,6 +225,7 @@ class ColumnSchemaBuilder extends Object
     /**
      * Builds the unsigned string for column.
      * @return string a string containing UNSIGNED keyword.
+     * @since 2.0.7
      */
     protected function buildUnsignedString()
     {

framework/db/Command.php

@@ -18,8 +18,9 @@ use yii\base\NotSupportedException;
  * The SQL statement it represents can be set via the [[sql]] property.
  *
  * To execute a non-query SQL (such as INSERT, DELETE, UPDATE), call [[execute()]].
- * To execute a SQL statement that returns result data set (such as SELECT),
+ * To execute a SQL statement that returns a result data set (such as SELECT),
  * use [[queryAll()]], [[queryOne()]], [[queryColumn()]], [[queryScalar()]], or [[query()]].
+ *
  * For example,
  *
  * ```php
@@ -33,7 +34,7 @@ use yii\base\NotSupportedException;
  * You may also call [[prepare()]] explicitly to prepare a SQL statement.
  *
  * Command also supports building SQL statements by providing methods such as [[insert()]],
- * [[update()]], etc. For example,
+ * [[update()]], etc. For example, the following code will create and execute an INSERT SQL statement:
  *
  * ```php
  * $connection->createCommand()->insert('user', [
@@ -42,9 +43,9 @@ use yii\base\NotSupportedException;
  * ])->execute();
  * ```
  *
- * To build SELECT SQL statements, please use [[QueryBuilder]] instead.
+ * To build SELECT SQL statements, please use [[Query]] instead.
  *
- * @see http://www.yiiframework.com/doc-2.0/guide-db-dao.html
+ * For more details and usage information on Command, see the [guide article on Database Access Objects](guide:db-dao).
  *
  * @property string $rawSql The raw SQL with parameter values inserted into the corresponding placeholders in
  * [[sql]]. This property is read-only.

framework/db/Query.php

@@ -35,6 +35,10 @@ use yii\base\Component;
  * $rows = $command->queryAll();
  * ```
  *
+ * Query internally uses the [[QueryBuilder]] class to generate the SQL statement.
+ *
+ * A more detailed usage guide on how to work with Query can be found in the [guide article on Query Builder](guide:db-query-builder).
+ *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @author Carsten Brandt <mail@cebe.cc>
  * @since 2.0

framework/db/QueryBuilder.php

@@ -13,8 +13,9 @@ use yii\base\NotSupportedException;
 /**
  * QueryBuilder builds a SELECT SQL statement based on the specification given as a [[Query]] object.
  *
- * QueryBuilder can also be used to build SQL statements such as INSERT, UPDATE, DELETE, CREATE TABLE,
- * from a [[Query]] object.
+ * SQL statements are created from [[Query]] objects using the [[build()]]-method.
+ *
+ * QueryBuilder is also used by [[Command]] to build SQL statements such as INSERT, UPDATE, DELETE, CREATE TABLE.
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0

framework/db/mssql/QueryBuilder.php

@@ -223,14 +223,8 @@ class QueryBuilder extends \yii\db\QueryBuilder
     }
 
     /**
-     * Builds SQL for IN condition
-     *
-     * @param string $operator
-     * @param array $columns
-     * @param Query $values
-     * @param array $params
-     * @return string SQL
-     * @throws NotSupportedException
+     * @inheritdoc
+     * @throws NotSupportedException if `$columns` is an array
      */
     protected function buildSubqueryInCondition($operator, $columns, $values, &$params)
     {

framework/db/mysql/Schema.php

@@ -243,7 +243,6 @@ class Schema extends \yii\db\Schema
     /**
      * Collects the foreign key column details for the given table.
      * @param TableSchema $table the table metadata
-     * @throws \Exception
      */
     protected function findConstraints($table)
     {

framework/db/sqlite/QueryBuilder.php

@@ -309,14 +309,8 @@ class QueryBuilder extends \yii\db\QueryBuilder
     }
 
     /**
-     * Builds SQL for IN condition
-     *
-     * @param string $operator
-     * @param array $columns
-     * @param Query $values
-     * @param array $params
-     * @return string SQL
-     * @throws NotSupportedException
+     * @inheritdoc
+     * @throws NotSupportedException if `$columns` is an array
      */
     protected function buildSubqueryInCondition($operator, $columns, $values, &$params)
     {