So I looked at the documentation but cannot find what I a looking for. I used placeholders to make things work a bit better for me, but I am running into some issues and wonder if I am not making a mistake.

I made a query:

SELECT '%VAR1%', price_usd * (SELECT exchange_rate FROM jgd_exchangerate WHERE exchange_rate_id = '%VAR2%') FROM jgd_prices WHERE price_id='%VAR3%'

Which works fine if I use the values instead of the placeholders.
I predefined values for all the three VAR's

If I use the short code without setting any parameters it kind of works, but if I use variables it does not work, it throws out an php error.

It seems that if I want to use a placeholder before the FROM statement those placeholders don't work, if I use them after the FROM statement no problems.

How can this be fixed?

Thank You in advance for your answer

Jan