1. 第一个语句定义了path这个名字所代表的字段的显示长度2. 是3. 表示在' '的左边补充空格直至总长度为level*3个字符4. 表示表的自连接操作5. 没有错误,运行结果如下:
idle>column path format a50;
idle>select level,sys_connect_by_path(child,'/') path
2 from hier
3 start with parent is null
4 connect by prior child = parent; LEVEL PATH
---------- --------------------------------------------------
1 /Asia
2 /Asia/China
3 /Asia/China/Beijing
2 /Asia/Japan
3 /Asia/Japan/Osaka
3 /Asia/Japan/Tokyo
1 /Australia
2 /Australia/New South Wales
3 /Australia/New South Wales/Sydney
1 /Europe
2 /Europe/United Kingdom
3 /Europe/United Kingdom/England
4 /Europe/United Kingdom/England/London
1 /North America
2 /North America/Canada
3 /North America/Canada/Ontario
4 /North America/Canada/Ontario/Ottawa
4 /North America/Canada/Ontario/Toronto
2 /North America/USA
3 /North America/USA/California
4 /North America/USA/California/Redwood Shores已选择21行。
idle>column path format a50;
idle>select level,sys_connect_by_path(child,'/') path
2 from hier
3 start with parent is null
4 connect by prior child = parent; LEVEL PATH
---------- --------------------------------------------------
1 /Asia
2 /Asia/China
3 /Asia/China/Beijing
2 /Asia/Japan
3 /Asia/Japan/Osaka
3 /Asia/Japan/Tokyo
1 /Australia
2 /Australia/New South Wales
3 /Australia/New South Wales/Sydney
1 /Europe
2 /Europe/United Kingdom
3 /Europe/United Kingdom/England
4 /Europe/United Kingdom/England/London
1 /North America
2 /North America/Canada
3 /North America/Canada/Ontario
4 /North America/Canada/Ontario/Ottawa
4 /North America/Canada/Ontario/Toronto
2 /North America/USA
3 /North America/USA/California
4 /North America/USA/California/Redwood Shores已选择21行。
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