9.SELECT idFROM flights AS fWHERE distance < (SELECT AVG(...[作者空间]
1.表中的任何列都可以作为主键， 只要它满足以下条件：任意两行都不具有相同的主键值；每一行都必须具有一个主键值（ ...[作者空间]
1.UPDATE celebsSET age = 22 WHERE id = 1; SELECT * FROM c...[作者空间]
9.SELECT idFROM flights AS fWHERE distance < (SELECT AVG(...[作者空间]
1.UPDATE celebsSET age = 22 WHERE id = 1; SELECT * FROM c...[作者空间]
