cross_join.md

# Cross Join

Joe 需要生成 goods 表

```mysql
create table goods(
    id int primary key auto_increment,
    category varchar(64),
    name varchar(256),
    price decimal(12, 4),
    stock int,
    upper_time timestamp
)
```

中所有T恤（category为`T-Shirt`）的所有尺寸，尺寸信息在 size 表

```mysql
create table size(
    id int primary key auto_increment,
    name varchar(16)
)
```

中，那么这个查询应该是：

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## 答案

```mysql
select g.id, g.name, s.name as size
from goods as g
    cross join size as s
where g.category = 'T-Shirt';
```

## 选项

### A

```mysql
select g.id, g.name, s.name as size
from goods as g
    full join size as s
where g.category = 'T-Shirt';
```

### B

```mysql
select g.id, g.name, s.name as size
from goods as g
    left join size as s
where g.category = 'T-Shirt';
```

### C

```mysql
select g.id, g.name, s.name as size
from goods as g
    left join size as s
where g.category = 'T-Shirt';
```

### D

```mysql
select g.id, g.name, s.name as size
from goods as g
    right join size as s
where g.category = 'T-Shirt';
```

### E

```mysql
select g.id, g.name, s.name as size
from goods as g
    outter join size as s
where g.category = 'T-Shirt';
```