一些带有EXISTS 或 NOT EXISTS谓词的子查询不能被其他形式的子查询等价交换,但所有带IN谓词、比较运算符、ANY、ALL谓词的子查询都能带EXISTS谓词的子查询等价交换 SELECT Sno,Sname,Sdept FROM Student WHERE Sdept IN( SELECT Sdept FROM Student WHERE Sname='刘晨'--; ); 上面这个3.55的例子就可以替换成以下 SE...
DataFrame df = sqlContext.sql("select count(*) from wangke.wangke where ns_date=20161224"); sqlContext.refreshTable("my_table") //(if configured,sparkSQL caches metadata) sqlContext.sql("CREATE TABLE IF NOT EXISTS src (key INT, value STRING)"); sqlContext.sql("LOAD DATA LOCAL INPATH ...
与例1 类似,在 SELECT 语句中使用 NOT IN 关键字,查询没有学习 Java 课程的学生姓名,SQL 语句和运行结果如下。 mysql> SELECT name FROM tb_students_info -> WHERE course_id NOT IN (SELECT id FROM tb_course WHERE course_name = 'Java'); +---+ | name | +---+ | Green | | Jane | | ...
10.udf Spark官方UDF使用文档:Spark SQL, Built-in Functions 11.空值 表A需要筛选出a中不等于aaa的数据(a字段有空值) 错误:select * from A where a != 'aaa'(空值数据也被过滤了) 正确:select * from A where (a != 'aaa' or a is null) 12.ARRAY的相关操作 生成:collect_set(struct(a.lesson...
rdd1.join(rdd2).filter{case(key,(v1,v2)=>{key==1})}sparksql select*from t_table1 a join t_table2 b on a.x=b.x where a.id=1底层是 先过滤再笛卡尔乘积,若干底层优化。 rdd1.filter(xxx)==>1join rdd2.filter(xxx)==>1
SELECT user_id, pay_time, money, order_id FROM (SELECT user_id, money, pay_time, order_id, row_number() over (PARTITION BY user_id ORDER BY pay_time) rank FROM test_db.order WHERE date_format(pay_time,'yyyy-MM') = '2020-10') t WHERE rank = 1; ...
14、when操作 1、连接本地spark import pandas as pd from pyspark.sql import SparkSession spark = SparkSession schema=['name','length']) dat
As a side note, if you’re not familiar with kaggle.com, it hosts ML competitions online, where almost 500,000 data scientists from around the world compete for monetary prizes or a chance to interview at one of the top ML companies. I’ve competed in five Kaggle competi...
使用以下原始 NoSQL 查询字符串查询数据:SELECT * FROM cosmosCatalog.cosmicworks.products WHERE price > 800 Python # Render results of raw queryrawQuery ="SELECT * FROM cosmosCatalog.cosmicworks.products WHERE price > 800"rawDf = spark.sql(rawQuery) rawDf.show() ...
val teenagerNamesDF = spark.sql("SELECT name FROM people WHERE age BETWEEN 13 AND 19") teenagerNamesDF.show() +---+ | name| +---+ |Justin| +---+ 3、MySQL Spark SQL可以通过JDBC从关系型数据库中读取数据的方式创建DataFrame,通过对DataFrame一系列的计算后,还可以将数据再写回关系型数据库中...