Table: guaran_notes
Columns: value
color
obverse
reverse
first_issued

Question: When was Color of green first issued?
SQL: SELECT MIN("first_issued") FROM guaran_notes WHERE "color" = 'green'

Question: When was Color of green last issued?
SQL: SELECT MAX("first_issued") FROM guaran_notes WHERE "color" = 'green'

Question: What reverse has a color of green?
SQL: SELECT "reverse" FROM guaran_notes WHERE "color" = 'green'

Question: How much was a Reverse of guitar of agustín pío barrios before 1998?
SQL: SELECT "value" FROM guaran_notes WHERE "first_issued" < 1998 AND "reverse" = 'guitar of agustín pío barrios'