# PREDICT BY
#### 功能描述
利用完成训练的模型进行推测任务。
#### 注意事项
调用的模型名称在系统表gs_model_warehouse中可查看到。
#### 语法格式
```
PREDICT BY model_name (FEATURES attribute [, attribute]...);
```
#### 参数说明
- **model_name**
  用于推测任务的模型名称。
  取值范围：字符串，需要符合[标识符命名规范](https://support.huaweicloud.com/centralized-devg-v3-gaussdb/gaussdb-42-0327.html#ZH-CN_TOPIC_0000002235339153__zh-cn_topic_0000002235101877_section1257443811315)。
  
- **attribute**
  推测任务的输入特征列名。
  取值范围：字符串，需要符合[标识符命名规范](https://support.huaweicloud.com/centralized-devg-v3-gaussdb/gaussdb-42-0327.html#ZH-CN_TOPIC_0000002235339153__zh-cn_topic_0000002235101877_section1257443811315)。
  
 
#### 示例
```
--创建数据表
gaussdb=# CREATE TABLE houses (
id INTEGER,
tax INTEGER,
bedroom INTEGER,
bath DOUBLE PRECISION,
price INTEGER,
size INTEGER,
lot INTEGER,
mark text
);
--插入训练数据
gaussdb=# INSERT INTO houses(id, tax, bedroom, bath, price, size, lot, mark) VALUES
(1,590,2,1,50000,770,22100,'a+'),
(2,1050,3,2,85000,1410,12000,'a+'),
(3,20,2,1,22500,1060,3500,'a-'),
(4,870,2,2,90000,1300,17500,'a+'),
(5,1320,3,2,133000,1500,30000,'a+'),
(6,1350,2,1,90500,850,25700,'a-'),
(7,2790,3,2.5,260000,2130,25000,'a+'),
(8,680,2,1,142500,1170,22000,'a-'),
(9,1840,3,2,160000,1500,19000,'a+'),
(10,3680,4,2,240000,2790,20000,'a-'),
(11,1660,3,1,87000,1030,17500,'a+'),
(12,1620,3,2,118500,1250,20000,'a-'),
(13,3100,3,2,140000,1760,38000,'a+'),
(14,2090,2,3,148000,1550,14000,'a-'),
(15,650,3,1.5,65000,1450,12000,'a-');
--训练模型
gaussdb=# CREATE MODEL price_model USING logistic_regression
 FEATURES size, lot
 TARGET mark
 FROM HOUSES
 WITH learning_rate=0.88, max_iterations=default;
——预测
gaussdb=# SELECT id, PREDICT BY price_model (FEATURES size,lot) FROM houses;
--删除模型
gaussdb=# DROP MODEL price_model;
--删除表
gaussdb=# DROP TABLE houses;
```
#### 相关链接
[CREATE MODEL](https://support.huaweicloud.com/centralized-devg-v3-gaussdb/gaussdb-42-0541.html#ZH-CN_TOPIC_0000002200579062)，[DROP MODEL](https://support.huaweicloud.com/centralized-devg-v3-gaussdb/gaussdb-42-0593.html#ZH-CN_TOPIC_0000002200419354)