MYSQL多表查询
1、两种方式
1、select 字段名列表 from 表名列表; (笛卡尔积)
t1 : name -> "A1" "A2" "A3"
t2 : name -> "B1" "B2"
select * from t1,t2;
+------+-------+
| name | name2 |
+------+-------+
| A1 | B1 |
| A1 | B2 |
| A2 | B1 |
| A2 | B2 |
| A3 | B1 |
| A3 | B2 |
+------+-------+
2、... where 条件;
2、练习
1、显示省和市的详细信息
河北省 石家庄市
河北省 廊坊市
湖北省 武汉市
select sheng.s_name,city.c_name from sheng,city
where
sheng.s_id=city.cfather_id;
2、显示省市县详细信息
select sheng.s_name as sheng,city.c_name as city,xian.x_name as xian from sheng,city,xian
where
sheng.s_id=city.cfather_id and
city.c_id=xian.xfather_id;
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