Count with distinct in hive
WebAug 6, 2013 · Yes, it is almost correct. But you have one simple mistake. Your column name is wrong inside COUNT. SELECT columnA,columnB,COUNT (DISTINCT columnC) No_of_distinct_colC from table_name group by columnA,columnB. Share. Improve this … WebApr 10, 2024 · 本篇教程介绍了大数据统计分析 Hive SQL count（distinct）效率问题及优化，希望阅读本篇文章以后大家有所收获，帮助大家对大数据云计算大数据分析的理解更加深入。 一个工作任务，统计一个按天分区每天都有百亿条数据条的hive表中account字段的非重用 …
Count with distinct in hive
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WebApr 6, 2024 · To count the number of distinct products sold in the year 2024, we can use the following SQL query: SELECT COUNT(DISTINCT prod) FROM product_mast WHERE year = 2024; Output : count --------- … WebNov 28, 2024 · Distinct support in Hive 2.1.0 and later (see HIVE-9534) Distinct is supported for aggregation functions including SUM, COUNT and AVG, which aggregate over the distinct values within each partition. Current implementation has the limitation that no ORDER BY or window specification can be supported in the partitioning clause for …
WebExample of GROUP BY Clause in Hive. Let's see an example to sum the salary of employees based on department. Select the database in which we want to create a table. hive> use hiveql; Now, create a table by using the following command: hive> create table emp (Id int, Name string , Salary float, Department string) row format delimited. WebJan 1, 2024 · Note: Most of these functions ignore NULL values. Below are some of the examples we will see in ...
Webapprox_count_distinct. aggregate function. Returns the estimated number of distinct values in expr within the group. The implementation uses the dense version of the HyperLogLog++ (HLL++) algorithm, a state of the art cardinality estimation algorithm. Results are accurate within a default value of 5%, which derives from the value of the … WebApr 7, 2024 · 注意事项 Group By数据倾斜 Group By也同样存在数据倾斜的问题，设置hive.groupby.skewindata为true，生成的查询计划会有两个MapReduce Job，第一个Jo ... 当使用聚合函数count distinct完成去重计数时，处理值为空的情况会使Reduce产生很严重的数据倾斜，可以将空值单独处理 ...
WebFeb 17, 2014 · SELECT Hour(log_date), Count(DISTINCT cookieid) AS UNIQUE, Count(1) AS impressions FROM test1 GROUP BY Hour(log_date); But the results are not correct. …
WebJul 28, 2024 · DISTINCT keyword is used in SELECT statement in HIVE to fetch only unique rows. The row does not mean entire row in the table but it means “row” as per … china oil press machine hydraulicWebNDV Function. An aggregate function that returns an approximate value similar to the result of COUNT (DISTINCT col), the "number of distinct values". It is much faster than the combination of COUNT and DISTINCT, and uses a constant amount of memory and thus is less memory-intensive for columns with high cardinality. china oil refineryWebOct 26, 2024 · QUERY: Select count (distinct (concat (c1,c2))) as Key, sum (distinct (c3)) as Val FROM test; In HIve it is successfully executed but in impala i am getting the below … china oil price historyWebFeb 19, 2024 · NOTE : The output of count(*) and count(1) is same but the difference is in the time taken to execute the query. count(1) is faster/optimized than count(*) because: count(*) has to iterate through all the columns, But count(1) iterates through only one column. Check the time difference between count(*) and count(1) on big data-set. grainy shadesWeb我是说，如果您的配置单元版本不包含hive-287，则需要使用count（1）。 然后你必须从下载补丁。 如果您不想下载修补程序，或者您有HIVE-287，但代码不起作用，请使用以下方法：选择col1、col2、count（1）FROM table GROUP BY col1、col2tanks进行说明，但您的建议会输出my ... china oil reserves rankWebSELECT COUNT(DISTINCT name) FROM sql_distinct_count; 2. In the below example we have found distinct number of records from the id and name column. We are using count and distinct two times in a single query. Select count (distinct id) as ID, count (distinct name) as Name from sql_distinct_count; 3. grainy resolutionWebSep 1, 2024 · In HIVE, I tried getting the count of distinct rows in 2 methods, SELECT COUNT (*) FROM (SELECT DISTINCT columns FROM table); SELECT COUNT (DISTINCT columns) FROM table; Both are yielding DIFFERENT RESULTS. The count for the first query is greater than the second query. DISTINCT keyword is used in SELECT … grainy shadows sfm