从HTML表单中搜索多个MySQL表并按字母顺序返回数据

I'd like to search 3 separate tables I've created from 1 form and return the data in alphabetical order. Currently I can search 3 tables separately with use of a drop-down box (from my form) to select a table but I've fallen short at querying them simultaneously and returning all the data in alphabetical order. I've been trying to solve it but I'm struggling a lot.I'd like to search 3 separate tables I've creat