【大数据面试题】33 手写一个 Flink SQL 样例

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我们来看看 Flink SQL大概流程和样例：

流程：

1.创建流处理环境 StreamExecutionEnvironment env
2.创建表环境 StreamTableEnvironment.create(env);
3.创建 source表，sink 表
4.用 table API 编写查询 SQL（返回 Table 对象）
5.执行 sink executeInsert("sink")

代码样例：

import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.EnvironmentSettings;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.TableEnvironment;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;import static org.apache.flink.table.api.Expressions.$;public class SqlDemo2 {public static void main(String[] args) {StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();// 1.创建表环境// 1.1 方法 1
//        EnvironmentSettings settings = EnvironmentSettings.newInstance()
//                .inStreamingMode()
//                .build();
//        TableEnvironment tableEnv = TableEnvironment.create(settings);// 1.2 方法 2StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);// 创建表// 用 datagen 生成随机数据作为 sourcetableEnv.executeSql("CREATE TABLE source (\n" +"    id INT\n" +"    ,ts BIGINT\n" +"    ,vc INT\n" +") WITH (\n" +"    'connector' = 'datagen'\n" +"    ,'rows-per-second'='1'\n" +"    ,'fields.id.kind'='random'\n" +"    ,'fields.id.min'='1'\n" +"    ,'fields.id.max'='10'\n" +"    ,'fields.ts.kind'='sequence'\n" +"    ,'fields.ts.min'='1'\n" +"    ,'fields.ts.max'='1000000'\n" +"    ,'fields.vc.kind'='random'\n" +"    ,'fields.vc.min'='1'\n" +"    ,'fields.vc.max'='100'\n" +");\n");tableEnv.executeSql("CREATE TABLE sink(\n" +"    id INT,\n" +"    sumVC INT,\n" +") WITH (\n" +"'connector'='print'\n" +");\n");// 执行查询Table source = tableEnv.from("source");Table select = source.where($("id").isGreater(5)).groupBy($("id")).aggregate($("vc").sum().as("sumVC")).select($("id"), $("sumVC"));// 执行 sinkselect.executeInsert("sink");}
}