$ zgrep -o '^CREATE.*' database_backup.sql.gz
CREATE TABLE `aa_migrations` ( CREATE TABLE `abcdefg_bar` ( CREATE TABLE `abcdefg_foo` ( CREATE TABLE `abcdefg_images` ( CREATE TABLE `abcdefg_table12` ( CREATE TABLE `abcdefg_table13` ( CREATE TABLE `abcdefg_table14` ( CREATE TABLE `abcdefg_table15` ( CREATE TABLE `abcdefg_users` (
You could also just count them:
$ zgrep -o '^CREATE.*' database_backup.sql.gz | wc -l 9