loop.md

# 循环

下面哪一项定义的函数可以生成指定范围内的整数数列？

## 答案

```postgresql
create function gen(start integer, stop integer) returns setof integer as $$
begin 
    for idx in start .. stop loop
        return next idx;
    end loop;
end;
$$ language plpgsql;
```

## 选项

### A

```postgresql
create function gen(start integer, stop integer) returns integer as $$
begin 
    for idx in start .. stop loop
        return idx;
    end loop;
end;
$$ language plpgsql;
```

### B

```postgresql
create function gen(start integer, stop integer) returns integer as $$
begin 
    for idx in start .. stop loop
        yield idx;
    end loop;
end;
$$ language plpgsql;
```

### C

```postgresql
create function gen(start integer, stop integer) returns setof integer as $$
begin 
    for idx in start .. stop loop
        return idx;
        idx += 1;
    end loop;
end;
$$ language plpgsql;
```

### D

```postgresql
create function gen(start integer, stop integer) returns setof integer as $$
begin 
    for idx in start .. stop loop
        select idx;
    end loop ;
end;
$$ language plpgsql;
```