Last year I was asked to optimize a code in our legacy portal (yet to be replaced with the new portal). The legacy system didn't have a design phase. Straight away went to development by whatever developer available at that time.
It was seriously fucked up.

So I went and had a look at the vanilla PHP code that served data for a datatable.
** I nearly fainted **

A query was done to get data from a table without any joins.
Then for loop to display those data.
Then inside for loop, for every single column that gets data from a related table there's a fucking query.
Eg: select * from users where.... to display username. Then again select * from users where..... to display user's email, then another query for his phone number. Then another query to get service providers name, then another to get their phone number.

I think the guy who did it wrote his first hello world app with a bunch of queries and sent it to production. No one bothered to check until 4 years later when it slowed down like a friggin snail.
I'm surprised it even survived that long.