Table: schools_riverhead
Columns: school
location
enrolment
founded
denomination
day_boarding
school_colours
abbreviation
in_competition_since

Question: How many schools have an enrollment of 850?
SQL: SELECT COUNT("founded") FROM schools_riverhead WHERE "enrolment" = 850

Question: What is the location of the school named Brisbane Girls' Grammar School?
SQL: SELECT "location" FROM schools_riverhead WHERE "school" = 'Brisbane Girls'' Grammar School'

Question: How many schools are located in South Brisbane?
SQL: SELECT COUNT("school") FROM schools_riverhead WHERE "location" = 'South Brisbane'

Question: When was SPLC founded?
SQL: SELECT MIN("founded") FROM schools_riverhead WHERE "abbreviation" = 'SPLC'

Question: What is the enrollment of STM which has been in competition since 1990?
SQL: SELECT COUNT("enrolment") FROM schools_riverhead WHERE "in_competition_since" = 1990 AND "abbreviation" = 'STM'