Kate Marshall

I’m currently working a full time job and bring home after tax £1,800. I’m looking at taking up a 0 hour contract as a second income on my days off. Some months I could earn up to £1300 and on other months earn £100 I currently pay national insurance and pension on my full time job as well as tax. Could I be advised on how my second job will affect my take home income from my full time job or will it only affect my second job take home. If it does affect either what percentage of tax will it change too ? Will it effect my tax code on my main job?