documentation review

README.md

@@ -1,2 +1,12 @@
 # mysql
 
+## dump
+
+```bash
+DB_HOST="127.0.0.1"
+DB_NAME="dbname"
+DB_USER="dbuser"
+DB_PASSWORD="123456"
+TARGET_FILENAME=${DB_NAME}_dump_$(date -d "today" +"%Y%m%d%H%M%S").sql
+mysqldump -v -h $DB_HOST --user=$DB_USER -p"$DB_PASSWORD" $DB_NAME > $TARGET_FILENAME
+```