CREATE TABLE "challenger_limited_selected_clients" (
  "client" text,
  "years_of_operation" text,
  "area_of_operation" text,
  "country" text,
  "services" text
);

Question: Where is the area of operation that had drilling during the year 1999?
SQL: SELECT "area_of_operation" FROM "challenger_limited_selected_clients" WHERE "services"='drilling' AND "years_of_operation"='1999';

Question: What country did the client Agiba-agip work in?
SQL: SELECT "country" FROM "challenger_limited_selected_clients" WHERE "client"='agiba-agip';

Question: What years was soc a client?
SQL: SELECT "years_of_operation" FROM "challenger_limited_selected_clients" WHERE "client"='soc';

Question: What years was El Mabrouk the area of operation?
SQL: SELECT "years_of_operation" FROM "challenger_limited_selected_clients" WHERE "area_of_operation"='el mabrouk';

Question: What services were in the area of operation Wadi Borjuj?
SQL: SELECT "services" FROM "challenger_limited_selected_clients" WHERE "area_of_operation"='wadi borjuj';