def generate_drop_table_statement(table, psql_schema_name, table_name_prefix):
    """ return drop table statement.
    params:
    table -- 'SqlTable' object
    psql_schema_name -- schema name in postgres where to drop table
    table_name_prefix -- table prefix, like 'yyyxxx_'"""
    if len(psql_schema_name):
        psql_schema_name += '.'
    query = 'DROP TABLE IF EXISTS %s"%s%s";' \
        % (psql_schema_name, table_name_prefix, table.table_name)
    return query