Hive select distinct one column

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The notation COUNT(column_name) only considers rows where the column contains a non-NULL value. You can also combine COUNT with the DISTINCT operator to eliminate duplicates before counting, and to count the combinations of values across multiple columns. When the query contains a GROUP BY clause, returns one value for each combination of ... I have a hive table that looks like this (total 460 columns) colA colB ..... ce_id filename ..... dt v j 4 gg 40 v j 5 gg ... DISTINCT or dropDuplicates is used to remove duplicate rows in the Dataframe. Row consists of columns, if you are selecting only one column then output will be unique values for that specific column. DISTINCT is very commonly used to seek possible values which exists in the dataframe for any given column. Answered November 18, 2016 · Author has 88 answers and 256K answer views. 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. Dec 28, 2019 · select emp_no,dept_no,avg(salary) from employee where emp_no in (14979,51582,10001,10002) group by emp_no,dept_no; This is because each employee may have worked in more than one department. that is why we cannot include dept_id in GROUP BY. Use case I. This is one of a use case where we can use COLLECT_SET and COLLECT_LIST. For example, the following is possible because count (DISTINCT) and sum (DISTINCT) specify the same column: INSERT OVERWRITE TABLE pv_gender_agg SELECT pv_users.gender, count (DISTINCT pv_users.userid), count (*), sum (DISTINCT pv_users.userid) FROM pv_users GROUP BY pv_users.gender; this is problematic, since I need to receive both X and Y but with X distinct. In some DBs this can be done using "select distinct on x,y from tabel" but hive dosent support "distinct on" – Tomer Sep 25 '11 at 8:37 this is problematic, since I need to receive both X and Y but with X distinct. In some DBs this can be done using "select distinct on x,y from tabel" but hive dosent support "distinct on" – Tomer Sep 25 '11 at 8:37 this is problematic, since I need to receive both X and Y but with X distinct. In some DBs this can be done using "select distinct on x,y from tabel" but hive dosent support "distinct on" – Tomer Sep 25 '11 at 8:37 Sep 10, 2013 · Hive supports array type columns so that you can store a list of values for a row all inside a single column, and better yet can still be queried. This is particularly useful to me in order to reduce the number of data rows in our database. Assume the name of hive table is “transact_tbl” and it has one column named as “connections”, and values in connections column are comma separated and total two commas are present in each value. Step 1: Create Hive Table. Create an input table transact_tbl in bdp schema using below command. Feb 26, 2020 · COUNT() function and SELECT with DISTINCT on multiple columns. You can use the count() function in a select statement with distinct on multiple columns to count the distinct rows. Here is an example: SELECT COUNT(*) FROM ( SELECT DISTINCT agent_code, ord_amount,cust_code FROM orders WHERE agent_code='A002'); Output: <Select Clause> <rferenced Columns> from <table_name> Group By <The columns on which we want to group the data> Select department, count(*) from the university.college Group By department; Here the department refers to one of the columns of the college table which is present in the university database and its value is various in departments ... <Select Clause> <rferenced Columns> from <table_name> Group By <The columns on which we want to group the data> Select department, count(*) from the university.college Group By department; Here the department refers to one of the columns of the college table which is present in the university database and its value is various in departments ... DISTINCT specifies removal of duplicate rows from the case set. Note, Hive sustains SELECT DISTINCT * starting in release 1.1.0 . let query4 = hiveQuery {for line in context.sample_08 do where (line.total_emp ?> 1000) maxBy line.salary} ALL and DISTINCT can also exist used in a UNION clause– see Union Syntax for more information. Feb 26, 2020 · Output : Number of employees ----- 25 Pictorial Presentation: SQL COUNT( ) with All . In the following, we have discussed the usage of ALL clause with SQL COUNT() function to count only the non NULL value for the specified column within the argument. Nov 28, 2017 · 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 performance reason. SELECT count(*) AS distinct_service_type FROM (SELECT distinct service_type FROM service_table) a; In this case, the first stage of the query implementing DISTINCT can use more than one reducer. In the second stage, the mapper will have less output just for the COUNT purpose since the data is already unique after implementing DISTINCT. Sep 25, 2020 · select isnotnull( NULL ); Hive CASE conditional function examples. select case x when 1 then 'one' when 2 then 'two' when 0 then 'zero' else 'out of range' end from t1; select case when dayname(now()) in ('Saturday','Sunday') then 'result undefined on weekends' when x > y then 'x greater than y' when x = y then 'x and y are equal' when x is null or y is null then 'one of the columns is null ... this is problematic, since I need to receive both X and Y but with X distinct. In some DBs this can be done using "select distinct on x,y from tabel" but hive dosent support "distinct on" – Tomer Sep 25 '11 at 8:37 — Returns the unique values from one column. — NULL is included in the set of values if any rows have a NULL in this column. select distinct c_birth_country from Employees; — Returns the unique combinations of values from multiple columns. select distinct c_salutation, c_last_name from Employees; Feb 27, 2019 · Note, Hive supports SELECT DISTINCT * starting in release 1.1.0 (HIVE-9194). hive> SELECT col1, col2 FROM t1 1 3 1 3 1 4 2 5 hive> SELECT DISTINCT col1, col2 FROM t1 1 3 1 4 2 5 hive> SELECT DISTINCT col1 FROM t1 1 2 ALL and DISTINCT can also be used in a UNION clause – see Union Syntax for more information. Teams. Q&A for Work. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Learn more select DISTINCT in HIVE 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 column listed in the SELECT statement. If the SELECT has 3 columns listed then SELECT DISTINCT will fetch unique row for those 3 column values only. SELECT DISTINCT c_birth_country FROM customer; -- Returns the unique combinations of values from multiple columns. SELECT DISTINCT c_salutation, c_last_name FROM customer; You can use DISTINCT in combination with an aggregation function, typically COUNT(), to find how many different values a column contains.-- Counts the unique values from one ... — Returns the unique values from one column. — NULL is included in the set of values if any rows have a NULL in this column. select distinct c_birth_country from Employees; — Returns the unique combinations of values from multiple columns. select distinct c_salutation, c_last_name from Employees; Sep 11, 2020 · This is one of the widely used methods to insert data into Hive table. We will use the SELECT clause along with INSERT INTO command to insert data into a Hive table by selecting data from another table. Below is the syntax of using SELECT statement with INSERT command. INSERT INTO TABLE tablename1 [PARTITION (partcol1=val1, partcol2=val2 ... SELECT DISTINCT c_birth_country FROM customer; -- Returns the unique combinations of values from multiple columns. SELECT DISTINCT c_salutation, c_last_name FROM customer; You can use DISTINCT in combination with an aggregation function, typically COUNT(), to find how many different values a column contains.-- Counts the unique values from one ...