} elseif ( 'returning' === strtolower( $query_args['customer_type'] ) ) {
				$customer_filter = " {$wpdb->prefix}wc_order_stats.returning_customer = 1";
			}
		}

		return $customer_filter;
	}

	/**
	 * Returns product attribute subquery elements used in JOIN and WHERE clauses,
	 * based on query arguments from the user.
	 *
	 * @param array  $query_args Parameters supplied by the user.
	 * @param string $table_name Database table name.
	 * @return array
	 */
	protected function get_attribute_subqueries( $query_args, $table_name ) {
		global $wpdb;

		$sql_clauses           = array(
			'join'  => array(),
			'where' => array(),
		);
		$match_operator        = $this->get_match_operator( $query_args );
		$post_meta_comparators = array(
			'='  => 'attribute_is',
			'!=' => 'attribute_is_not',
		);

		foreach ( $post_meta_comparators as $comparator => $arg ) {
			if ( ! isset( $query_args[ $arg ] ) || ! is_array( $query_args[ $arg ] ) ) {
				continue;
			}
			foreach ( $query_args[ $arg ] as $attribute_term ) {
				// We expect tuples.
				if ( ! is_array( $attribute_term ) || 2 !== count( $attribute_term ) ) {
					continue;
				}

				// If the tuple is numeric, assume these are IDs.
				if ( is_numeric( $attribute_term[0] ) && is_numeric( $attribute_term[1] ) ) {
					$attribute_id = intval( $attribute_term[0] );
					$term_id      = intval( $attribute_term[1] );

					// Invalid IDs.
					if ( 0 === $attribute_id || 0 === $term_id ) {
						continue;
					}

					// @todo: Use wc_get_attribute () instead ?
					$attr_taxonomy = wc_attribute_taxonomy_name_by_id( $attribute_id );
					// Invalid attribute ID.
					if ( empty( $attr_taxonomy ) ) {
						continue;
					}

					$attr_term = get_term_by( 'id', $term_id, $attr_taxonomy );
					// Invalid term ID.
					if ( false === $attr_term ) {
						continue;
					}

					$meta_key   = sanitize_title( $attr_taxonomy );
					$meta_value = $attr_term->slug;
				} else {
					// Assume these are a custom attribute slug/value pair.
					$meta_key   = esc_sql( $attribute_term[0] );
					$meta_value = esc_sql( $attribute_term[1] );
				}

				$join_alias = 'orderitemmeta1';

				if ( empty( $sql_clauses['join'] ) ) {
					$table_name            = esc_sql( $table_name );
					$sql_clauses['join'][] = "JOIN {$wpdb->prefix}woocommerce_order_items orderitems ON orderitems.order_id = {$table_name}.order_id";
				}

				// If we're matching all filters (AND), we'll need multiple JOINs on postmeta.
				// If not, just one.
				if ( 'AND' === $match_operator || 1 === count( $sql_clauses['join'] ) ) {
					$join_idx              = count( $sql_clauses['join'] );
					$join_alias            = 'orderitemmeta' . $join_idx;
					$sql_clauses['join'][] = "JOIN {$wpdb->prefix}woocommerce_order_itemmeta as {$join_alias} ON {$join_alias}.order_item_id = orderitems.order_item_id";
				}

				// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared
				$sql_clauses['where'][] = $wpdb->prepare( "( {$join_alias}.meta_key = %s AND {$join_alias}.meta_value {$comparator} %s )", $meta_key, $meta_value );
			}
		}

		// If we're matching multiple attributes and all filters (AND), make sure
		// we're matching attributes on the same product.
		$num_attribute_filters = count( $sql_clauses['join'] );

		for ( $i = 2; $i < $num_attribute_filters; $i++ ) {
			$join_alias            = 'orderitemmeta' . $i;
			$sql_clauses['join'][] = "AND orderitemmeta1.order_item_id = {$join_alias}.order_item_id";
		}

		return $sql_clauses;
	}

	/**
	 * Returns logic operator for WHERE subclause based on 'match' query argument.
	 *
	 * @param array $query_args Parameters supplied by the user.
	 * @return string
	 */
	protected function get_match_operator( $query_args ) {
		$operator = 'AND';

		if ( ! isset( $query_args['match'] ) ) {
			return $operator;
		}

		if ( 'all' === strtolower( $query_args['match'] ) ) {
			$operator = 'AND';
		} elseif ( 'any' === strtolower( $query_args['match'] ) ) {
			$operator = 'OR';
		}
		return $operator;
	}

	/**
	 * Returns filtered comma separated ids, based on query arguments from the user.
	 *
	 * @param array  $query_args Parameters supplied by the user.
	 * @param string $field      Query field to filter.
	 * @param string $separator  Field separator.
	 * @return string
	 */
	protected function get_filtered_ids( $query_args, $field, $separator = ',' ) {
		global $wpdb;

		$ids_str = '';
		$ids     = isset( $query_args[ $field ] ) && is_array( $query_args[ $field ] ) ? $query_args[ $field ] : array();

		/**
		 * Filter the IDs before retrieving report data.
		 *
		 * Allows filtering of the objects included or excluded from reports.
		 *
		 * @param array  $ids        List of object Ids.
		 * @param array  $query_args The original arguments for the request.
		 * @param string $field      The object type.
		 * @param string $context    The data store context.
		 */
		$ids = apply_filters( 'woocommerce_analytics_' . $field, $ids, $query_args, $field, $this->context );

		if ( ! empty( $ids ) ) {
			$placeholders = implode( $separator, array_fill( 0, count( $ids ), '%d' ) );
			/* phpcs:disable WordPress.DB.PreparedSQL.InterpolatedNotPrepared */
			$ids_str = $wpdb->prepare( "{$placeholders}", $ids );
			/* phpcs:enable */
		}
		return $ids_str;
	}

	/**
	 * Assign report columns once full table name has been assigned.
	 */
	protected function assign_report_columns() {}
}