今天要解决的问题是如何使用spark sql 建表，插入数据以及查询数据

1、建立一个类叫 DeltaLakeWithSparkSql1，具体代码如下，例子参考Delta Lake Up & Running第3章内容

import org.apache.spark.sql.SaveMode;
import org.apache.spark.sql.SparkSession;

import java.text.SimpleDateFormat;
import java.util.Date;

public class DeltaLakeWithSparkSql1 {
    public static void main(String[] args) {
        SparkSession spark = SparkSession.builder()
                .master("local[*]")
                .appName("delta_lake")
                .config("spark.sql.extensions", "io.delta.sql.DeltaSparkSessionExtension")
                .config("spark.sql.catalog.spark_catalog", "org.apache.spark.sql.delta.catalog.DeltaCatalog")
                .getOrCreate();
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");

        spark.sql("CREATE DATABASE IF NOT EXISTS taxidb");
        spark.sql("CREATE TABLE IF NOT EXISTS taxidb.YellowTaxi(" +
                "RideID INT,"+
                "PickupTime TIMESTAMP,"+
                "CabNumber STRING)" +
                "USING DELTA LOCATION 'file:///D:\\\\bigdata\\\\detla-lake-with-java\\\\YellowTaxi'"
        );
       // 插入5条记录
        spark.sql("DESCRIBE TABLE taxidb.YellowTaxi").show();
        spark.sql("INSERT INTO taxidb.YellowTaxi (RideID,PickupTime,CabNumber) values (1,'2013-10-13 10:13:15','51-96')");
        spark.sql("INSERT INTO taxidb.YellowTaxi (RideID,PickupTime,CabNumber) values (2,'2013-10-13 10:13:15','51-96')");
        spark.sql("INSERT INTO taxidb.YellowTaxi (RideID,PickupTime,CabNumber) values (3,'2013-10-13 10:13:15','51-96')");
        spark.sql("INSERT INTO taxidb.YellowTaxi (RideID,PickupTime,CabNumber) values (4,'2013-10-13 10:13:15','51-96')");
        spark.sql("INSERT INTO taxidb.YellowTaxi (RideID,PickupTime,CabNumber) values (5,'2013-10-13 10:13:15','51-96')");

        System.out.println("不分区查询开始时间（含毫秒）: " + sdf.format(new Date()));
        spark.sql("SELECT RideID,PickupTime,CabNumber FROM taxidb.YellowTaxi").show();
        System.out.println("不分区查询结束时间（含毫秒）: " + sdf.format(new Date()));

        spark.sql("CREATE TABLE IF NOT EXISTS taxidb.YellowTaxiPartitioned(" +
                "RideID INT,"+
                "PickupTime TIMESTAMP,"+
                "CabNumber STRING)" +
                "USING DELTA PARTITIONED BY(RideID) LOCATION 'file:///D:\\\\bigdata\\\\detla-lake-with-java\\\\YellowTaxiPartitioned'"
        );
        spark.sql("DESCRIBE TABLE taxidb.YellowTaxiPartitioned").show();
        var df=spark.read().format("delta").table("taxidb.YellowTaxi");
         //将数据复制到分区表
        df.write().format("delta").mode(SaveMode.Overwrite).save("file:///D:\\\\bigdata\\\\detla-lake-with-java\\\\YellowTaxiPartitioned");
        System.out.println("分区查询开始时间（含毫秒）: " + sdf.format(new Date()));
        spark.sql("SELECT RideID,PickupTime,CabNumber FROM taxidb.YellowTaxiPartitioned").show();
        System.out.println("分区查询结束时间（含毫秒）: " + sdf.format(new Date()));
        spark.close();
    }
}

代码主要实现建立一个表名为YellowTaxi，插入5条数据，然后查询YellowTaxi这5条数据，再建立一个表YellowTaxiPartitioned，YellowTaxiPartitioned是分区表。然后从YellowTaxi获取数据并写入到YellowTaxiPartitioned，再查询YellowTaxiPartitioned这5条数据

2、IDEA运行结果如下：

具体文字内容如下，从结果可以看出分区表的查询效率要比不分区表要好，后面建表还是要用分区表。

+----------+---------+-------+
|  col_name|data_type|comment|
+----------+---------+-------+
|    RideID|      int|   NULL|
|PickupTime|timestamp|   NULL|
| CabNumber|   string|   NULL|
+----------+---------+-------+

不分区查询开始时间（含毫秒）: 2024-05-01 11:29:39.655
+------+-------------------+---------+
|RideID|         PickupTime|CabNumber|
+------+-------------------+---------+
|     1|2013-10-13 10:13:15|    51-96|
|     2|2013-10-13 10:13:15|    51-96|
|     4|2013-10-13 10:13:15|    51-96|
|     3|2013-10-13 10:13:15|    51-96|
|     5|2013-10-13 10:13:15|    51-96|
+------+-------------------+---------+

不分区查询结束时间（含毫秒）: 2024-05-01 11:29:40.130

+--------------------+---------+-------+
|            col_name|data_type|comment|
+--------------------+---------+-------+
|              RideID|      int|   NULL|
|          PickupTime|timestamp|   NULL|
|           CabNumber|   string|   NULL|
|# Partition Infor...|         |       |
|          # col_name|data_type|comment|
|              RideID|      int|   NULL|
+--------------------+---------+-------+

分区查询开始时间（含毫秒）: 2024-05-01 11:29:42.052
+------+-------------------+---------+
|RideID|         PickupTime|CabNumber|
+------+-------------------+---------+
|     4|2013-10-13 10:13:15|    51-96|
|     3|2013-10-13 10:13:15|    51-96|
|     1|2013-10-13 10:13:15|    51-96|
|     2|2013-10-13 10:13:15|    51-96|
|     5|2013-10-13 10:13:15|    51-96|
+------+-------------------+---------+

分区查询结束时间（含毫秒）: 2024-05-01 11:29:42.198