The Seven Years' War was a conflict that took place during the reign of Redanian king Vestibor the Proud between Redania and Northern Coalition (inclouding Kaedwen, Temeria, Hengfors and Malleore) in 11th century post resurrection.
Short-term effect :
Which resulted in Redania fall heavily - coalition of Northern kingdoms (Malleore, Caingorn & Kaedwen (reign of Dagread likely) occupied fertile valleys of the rivers Buina and Nimnar and Temeria in south, conquered Novigrad and Pontar Delta until reign of king Radovid III. known as the Bold who (by war or negotiations) get his old borders back.
Long-term effect :
During negotiation between Radovid III and Temerian king (likely Goidemar) a compromise was reached, nor Redania or Temeria have Novigrad since that because city gains status of Free City.