match_fields.md

# 左匹配

Goods 表结构如下：

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

Joe 发现有大量查询 `select id, category_id, name, price from goods where name=? and category_id=?`，
性能很差，应该如何优化？

## 答案

将该查询改写为 

```mysql
select id, category_id, name, price from goods where category_id=? and name=?;
```

## 选项

### A

将该查询改写为

```mysql
select id, category_id, name, price from goods where category_id and name= (?, ?);
```

### B

将该查询改写为

```mysql
select id, category_id, name, price from goods where not (category_id !=? or name != ?);
```

### C

将该查询改写为

```mysql
select id, category_id, name, price from goods where not (category_id !=?) and not (name != ?);
```