# PREPARE
<a name="querying-with-prepared-statements-prepare"></a>

准备要在之后运行的语句。预准备语句将以您指定的名称保存在当前工作组中。语句可以包含参数来代替要在查询运行时替换的文字。要替换为值的参数用问号表示。

## 语法
<a name="querying-with-prepared-statements-prepare-syntax"></a>

```
PREPARE statement_name FROM statement
```

下表介绍了这些参数。


****  

| 参数 | 说明 | 
| --- | --- | 
| statement\$1name | 要执行的预准备语句的名称。此名称在工作组范围内必须唯一。 | 
| 语句 | SELECT、CTAS 或 INSERT INTO 查询。 | 

## PREPARE 示例
<a name="querying-with-prepared-statements-prepare-examples"></a>

以下示例将演示如何使用 `PREPARE` 语句。问号表示在运行查询时由 `EXECUTE` 语句提供的值。

```
PREPARE my_select1 FROM
SELECT * FROM nation
```

```
PREPARE my_select2 FROM
SELECT * FROM "my_database"."my_table" WHERE year = ?
```

```
PREPARE my_select3 FROM
SELECT order FROM orders WHERE productid = ? and quantity < ?
```

```
PREPARE my_insert FROM
INSERT INTO cities_usa (city, state)
SELECT city, state
FROM cities_world
WHERE country = ?
```

```
PREPARE my_unload FROM
UNLOAD (SELECT * FROM table1 WHERE productid < ?)
TO 's3://amzn-s3-demo-bucket/'
WITH (format='PARQUET')
```