如何在不索引列的情况下在innodb表中添加外键约束？

Question

i read some advice about table indexing, and i fount out that indexes should be introduced later when your sql queries are running slow..

my problem is I index almost all my columns in one table. this table is tied to other table, for example the users table column country is tied to the country table

user table          country table
id                  id
countryId           name

I added an index in the countryId column, so that I can link it to the country table's id because i can't create a foreign key constraints when I don't have an index on the column.

Basically i have many columns that are link to other table just to add constraints to my column.

for example, the country table is not more than 100, so if someone just accidentally inserted a value of 101, mysql won't accept that data because the country table only have 1-100..

So how can i avoid adding indexes and still have the function of table data constraints?

Answer 1

1. That advice is awful.

2. Index columns that you will be searching on or where you need particular constraints such as unique values.

The only reason NOT to add indexes is that they do take up space. But, unless you're working with so much data that you'll need a database administrator, you probably won't have to worry about it.