Table: yugoslav_cup_1990_91
Columns: tie_no
team_1
agg
team_2
1st_leg
2nd_leg

Question: Who is team 1 when team 2 is koper?
SQL: SELECT "team_1" FROM yugoslav_cup_1990_91 WHERE "team_2" = 'Koper'

Question: What is the tie when team 2 is koper?
SQL: SELECT MIN("tie_no") FROM yugoslav_cup_1990_91 WHERE "team_2" = 'Koper'

Question: How many 1st leg have team 1 ofk belgrade?
SQL: SELECT COUNT("1st_leg") FROM yugoslav_cup_1990_91 WHERE "team_1" = 'OFK Belgrade'

Question: How many tie no have team 1 as borac banja luka?
SQL: SELECT "tie_no" FROM yugoslav_cup_1990_91 WHERE "team_1" = 'Borac Banja Luka'