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 1 #全外
 2 use girls;
 3 SELECT b.*,a.*
 4 FROM beauty b
 5 FULL OUTER JOIN boys a
 6 on b.boyfrien_id=a.id;
 7 
 8 #交叉连接99标准笛卡尔乘积
 9 SELECT b.*,ob.*
10 FROM beauty b
11 CROSS JOIN boys ob;
12 
13 #sql92和sql99pk
14 #功能：sql99支持的较多
15 #可读性：sql99实现连接条件和筛选条件分离，可读性较高
16 
17 #一、查询编号>3的女神的男朋友信息，如果有则列出详细，如果没有，用nu11填充、
18 SELECT b.id,b.name,be.*
19 FROM beauty b
20 LEFT OUTER JOIN boys be
21 ON b.boyfriend_id=be.id
22 and b.id>3;
23 
24 #二、查询哪个城市没有部门
25 USE myemployees;
26 SELECT city
27 FROM locations l
28 LEFT OUTER JOIN departments d
29 on d.location_id=l.location_id
30 WHERE d.department_id is null;
31 
32 #三、查询部门名为SAM或IT的员工信息
33 SELECT e.*,d.department_name
34 FROM employees e
35 LEFT OUTER JOIN departments d
36 on e.department_id=d.department_id
37 WHERE d.department_name in('SAL','IT');