$this->query_where .= $this->get_search_sql( $search, $search_columns, $wild );
		}

		if ( ! empty( $include ) ) {
			// Sanitized earlier.
			$ids = implode( ',', $include );
			$this->query_where .= " AND $wpdb->users.ID IN ($ids)";
		} elseif ( ! empty( $qv['exclude'] ) ) {
			$ids = implode( ',', wp_parse_id_list( $qv['exclude'] ) );
			$this->query_where .= " AND $wpdb->users.ID NOT IN ($ids)";
		}

		// Date queries are allowed for the user_registered field.
		if ( ! empty( $qv['date_query'] ) && is_array( $qv['date_query'] ) ) {
			$date_query = new WP_Date_Query( $qv['date_query'], 'user_registered' );
			$this->query_where .= $date_query->get_sql();
		}

		/**
		 * Fires after the WP_User_Query has been parsed, and before
		 * the query is executed.
		 *
		 * The passed WP_User_Query object contains SQL parts formed
		 * from parsing the given query.
		 *
		 * @since 3.1.0
		 *
		 * @param WP_User_Query $this The current WP_User_Query instance,
		 *                            passed by reference.
		 */
		do_action_ref_array( 'pre_user_query', array( &$this ) );
	}

	/**
	 * Execute the query, with the current variables.
	 *
	 * @since 3.1.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 */
	public function query() {
		global $wpdb;

		$qv =& $this->query_vars;

		$this->request = "SELECT $this->query_fields $this->query_from $this->query_where $this->query_orderby $this->query_limit";

		if ( is_array( $qv['fields'] ) || 'all' == $qv['fields'] ) {
			$this->results = $wpdb->get_results( $this->request );
		} else {
			$this->results = $wpdb->get_col( $this->request );
		}

		/**
		 * Filters SELECT FOUND_ROWS() query for the current WP_User_Query instance.
		 *
		 * @since 3.2.0
		 *
		 * @global wpdb $wpdb WordPress database abstraction object.
		 *
		 * @param string $sql The SELECT FOUND_ROWS() query for the current WP_User_Query.
		 */
		if ( isset( $qv['count_total'] ) && $qv['count_total'] )
			$this->total_users = (int) $wpdb->get_var( apply_filters( 'found_users_query', 'SELECT FOUND_ROWS()' ) );

		if ( !$this->results )
			return;

		if ( 'all_with_meta' == $qv['fields'] ) {
			cache_users( $this->results );

			$r = array();
			foreach ( $this->results as $userid )
				$r[ $userid ] = new WP_User( $userid, '', $qv['blog_id'] );

			$this->results = $r;
		} elseif ( 'all' == $qv['fields'] ) {
			foreach ( $this->results as $key => $user ) {
				$this->results[ $key ] = new WP_User( $user, '', $qv['blog_id'] );
			}
		}
	}

	/**
	 * Retrieve query variable.
	 *
	 * @since 3.5.0
	 *
	 * @param string $query_var Query variable key.
	 * @return mixed
	 */
	public function get( $query_var ) {
		if ( isset( $this->query_vars[$query_var] ) )
			return $this->query_vars[$query_var];

		return null;
	}

	/**
	 * Set query variable.
	 *
	 * @since 3.5.0
	 *
	 * @param string $query_var Query variable key.
	 * @param mixed $value Query variable value.
	 */
	public function set( $query_var, $value ) {
		$this->query_vars[$query_var] = $value;
	}

	/**
	 * Used internally to generate an SQL string for searching across multiple columns
	 *
	 * @since 3.1.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string $string
	 * @param array  $cols
	 * @param bool   $wild   Whether to allow wildcard searches. Default is false for Network Admin, true for single site.
	 *                       Single site allows leading and trailing wildcards, Network Admin only trailing.
	 * @return string
	 */
	protected function get_search_sql( $string, $cols, $wild = false ) {
		global $wpdb;

		$searches = array();
		$leading_wild = ( 'leading' == $wild || 'both' == $wild ) ? '%' : '';
		$trailing_wild = ( 'trailing' == $wild || 'both' == $wild ) ? '%' : '';
		$like = $leading_wild . $wpdb->esc_like( $string ) . $trailing_wild;

		foreach ( $cols as $col ) {
			if ( 'ID' == $col ) {
				$searches[] = $wpdb->prepare( "$col = %s", $string );
			} else {
				$searches[] = $wpdb->prepare( "$col LIKE %s", $like );
			}
		}

		return ' AND (' . implode(' OR ', $searches) . ')';
	}

	/**
	 * Return the list of users.
	 *
	 * @since 3.1.0
	 *
	 * @return array Array of results.
	 */
	public function get_results() {
		return $this->results;
	}

	/**
	 * Return the total number of users for the current query.
	 *
	 * @since 3.1.0
	 *
	 * @return int Number of total users.
	 */
	public function get_total() {
		return $this->total_users;
	}

	/**
	 * Parse and sanitize 'orderby' keys passed to the user query.
	 *
	 * @since 4.2.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string $orderby Alias for the field to order by.
	 * @return string Value to used in the ORDER clause, if `$orderby` is valid.
	 */
	protected function parse_orderby( $orderby ) {
		global $wpdb;

		$meta_query_clauses = $this->meta_query->get_clauses();

		$_orderby = '';
		if ( in_array( $orderby, array( 'login', 'nicename', 'email', 'url', 'registered' ) ) ) {
			$_orderby = 'user_' . $orderby;
		} elseif ( in_array( $orderby, array( 'user_login', 'user_nicename', 'user_email', 'user_url', 'user_registered' ) ) ) {
			$_orderby = $orderby;
		} elseif ( 'name' == $orderby || 'display_name' == $orderby ) {
			$_orderby = 'display_name';
		} elseif ( 'post_count' == $orderby ) {
			// todo: avoid the JOIN
			$where = get_posts_by_author_sql( 'post' );
			$this->query_from .= " LEFT OUTER JOIN (
				SELECT post_author, COUNT(*) as post_count
				FROM $wpdb->posts
				$where
				GROUP BY post_author
			) p ON ({$wpdb->users}.ID = p.post_author)
			";
			$_orderby = 'post_count';
		} elseif ( 'ID' == $orderby || 'id' == $orderby ) {
			$_orderby = 'ID';
		} elseif ( 'meta_value' == $orderby || $this->get( 'meta_key' ) == $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value";
		} elseif ( 'meta_value_num' == $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value+0";
		} elseif ( 'include' === $orderby && ! empty( $this->query_vars['include'] ) ) {
			$include = wp_parse_id_list( $this->query_vars['include'] );
			$include_sql = implode( ',', $include );
			$_orderby = "FIELD( $wpdb->users.ID, $include_sql )";
		} elseif ( 'nicename__in' === $orderby ) {
			$sanitized_nicename__in = array_map( 'esc_sql', $this->query_vars['nicename__in'] );
			$nicename__in = implode( "','", $sanitized_nicename__in );
			$_orderby = "FIELD( user_nicename, '$nicename__in' )";
		} elseif ( 'login__in' === $orderby ) {
			$sanitized_login__in = array_map( 'esc_sql', $this->query_vars['login__in'] );
			$login__in = implode( "','", $sanitized_login__in );
			$_orderby = "FIELD( user_login, '$login__in' )";
		} elseif ( isset( $meta_query_clauses[ $orderby ] ) ) {
			$meta_clause = $meta_query_clauses[ $orderby ];
			$_orderby = sprintf( "CAST(%s.meta_value AS %s)", esc_sql( $meta_clause['alias'] ), esc_sql( $meta_clause['cast'] ) );
		}

		return $_orderby;
	}

	/**
	 * Parse an 'order' query variable and cast it to ASC or DESC as necessary.
	 *
	 * @since 4.2.0
	 *
	 * @param string $order The 'order' query variable.
	 * @return string The sanitized 'order' query variable.
	 */
	protected function parse_order( $order ) {
		if ( ! is_string( $order ) || empty( $order ) ) {
			return 'DESC';
		}

		if ( 'ASC' === strtoupper( $order ) ) {
			return 'ASC';
		} else {
			return 'DESC';
		}
	}

	/**
	 * Make private properties readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to get.
	 * @return mixed Property.
	 */
	public function __get( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return $this->$name;
		}
	}

	/**
	 * Make private properties settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name  Property to check if set.
	 * @param mixed  $value Property value.
	 * @return mixed Newly-set property.
	 */
	public function __set( $name, $value ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return $this->$name = $value;
		}
	}

	/**
	 * Make private properties checkable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to check if set.
	 * @return bool Whether the property is set.
	 */
	public function __isset( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			return isset( $this->$name );
		}
	}

	/**
	 * Make private properties un-settable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name Property to unset.
	 */
	public function __unset( $name ) {
		if ( in_array( $name, $this->compat_fields ) ) {
			unset( $this->$name );
		}
	}

	/**
	 * Make private/protected methods readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param callable $name      Method to call.
	 * @param array    $arguments Arguments to pass when calling.
	 * @return mixed Return value of the callback, false otherwise.
	 */
	public function __call( $name, $arguments ) {
		if ( 'get_search_sql' === $name ) {
			return call_user_func_array( array( $this, $name ), $arguments );
		}
		return false;
	}
}