Sample to running a custom SQL in "Docker Official MySQL Image"

docker-compose.yml

web:
    image: corbinu/docker-phpmyadmin
    ports:
        - "80:80"
    links:
        - mysql:mysql
    environment:
        MYSQL_USERNAME: root

mysql:
    image: mysql
    volumes:
        - ./initdb.d:/docker-entrypoint-initdb.d
    environment:
        MYSQL_ROOT_PASSWORD: mysqlpassword
        MYSQL_USER: "example_user"
        MYSQL_PASSWORD: "example_pass"
        MYSQL_DATABASE: "example"
    ports:
        - "3306:3306"

initdb.d-create_another_db.sh

#!/bin/bash -eu

mysql=( mysql --protocol=socket -uroot -p"${MYSQL_ROOT_PASSWORD}" )

"${mysql[@]}" <<-EOSQL
    CREATE DATABASE IF NOT EXISTS another_db;
    GRANT ALL ON another_db.* TO '${MYSQL_USER}'@'%' ;
EOSQL

initdb.d-create_table_in_exampledb.sql

CREATE TABLE IF NOT EXISTS `example`.`sample` (
  `id` INT UNSIGNED NOT NULL,
  `name` VARCHAR(255) NOT NULL,
  `created_at` DATETIME NOT NULL,
  PRIMARY KEY (`id`))
ENGINE = InnoDB;