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SQL操作:Select (SelectBatchOp)

Java 类名:com.alibaba.alink.operator.batch.sql.SelectBatchOp

Python 类名:SelectBatchOp

功能介绍

对批式数据进行sql的SELECT操作。

使用方式

SELECT 语句中支持的内置函数可以参考 Flink
对应版本的官方文档: System (Built-in) Functions
。 但需要注意,有些内置函数在旧 planner
中不支持,在这里列出:Unsupported Built-In Functions

参数说明

名称 中文名称 描述 类型 是否必须? 取值范围 默认值
clause 运算语句 运算语句 String

代码示例

Python 代码

df = pd.DataFrame([
    ['Ohio', 2000, 1.5],
    ['Ohio', 2001, 1.7],
    ['Ohio', 2002, 3.6],
    ['Nevada', 2001, 2.4],
    ['Nevada', 2002, 2.9],
    ['Nevada', 2003, 3.2]
])

batch_data = BatchOperator.fromDataframe(df, schemaStr='f1 string, f2 bigint, f3 double')
batch_data.link(SelectBatchOp().setClause("f1 as name")).print()

Java 代码

import com.alibaba.alink.operator.batch.BatchOperator;
import com.alibaba.alink.operator.batch.source.MemSourceBatchOp;
import com.alibaba.alink.operator.batch.sql.SelectBatchOp;
import org.junit.Test;

public class SelectBatchOpTest {
	@Test
	public void testSelectBatchOp() throws Exception {
        List <Row> df = Arrays.asList(
    	    Row.of("Ohio", 2000, 1.5),
    		Row.of("Ohio", 2001, 1.7),
    		Row.of("Ohio", 2002, 3.6),
    		Row.of("Nevada", 2001, 2.4),
    		Row.of("Nevada", 2002, 2.9),
    		Row.of("Nevada", 2003, 3.2)
    	);
    	BatchOperator <?> data = new MemSourceBatchOp(df, "f1 string, f2 int, f3 double");
		data.link(new SelectBatchOp().setClause("f1 as name")).print();
	}
}

运行结果

name

Ohio
Ohio
Ohio
Nevada
Nevada
Nevada