lateral-join | 易学教程

Get ranking of words over date based on frequency in PostgreSQL

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问题 I have a database that stores twitter data: Create Table tweet( ID BIGINT UNIQUE, user_ID BIGINT, created_at TIMESTAMPTZ, tweet TEXT; I'm trying to write a query that goes through the words in tweet for all rows gets the frequency of each word, and returns the top ten most frequent words along with the words' ranking over each date. Example: ("word1":[1,20,22,23,24,25,26,27,28,29,30,29,28,27,26,25,26,27,28,29,30,29,28,29,28,27,28,29,30,30,...], 'word2' [...]) My current query gets the top ten

What is the equivalent Syntax for Outer Apply in PostgreSQL [duplicate]

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问题 This question already has answers here : Postgres analogue to CROSS APPLY in SQL Server (4 answers) Closed 2 years ago . Im trying to find a SQL query on the equivalent usage of OUTER APPLY from MSSQL to PostgreSQL but it seems hard to find. My MSSQL sample query is like this. hope someone can help me with my problem. thanks in advance. SELECT table1.col1, table1.col2, Supp.ID, Supp.Supplier FROM SIS_PRS table1 OUTER APPLY (SELECT TOP 1 ID, SupplierName FROM table2 WHERE table2.ID = table1

What is the equivalent Syntax for Outer Apply in PostgreSQL [duplicate]

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Select from PostgreSQL function that returns composite type

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问题 How to include a function that returns a composite type in a SELECT ? I have composite type: CREATE TYPE public.dm_nameid AS ( id public.dm_int, name public.dm_str ); Also, I have a function that returns this type fn_GetLinkedProject(integer) . And I need to make something like this: SELECT p.id, p.data, p.name, pl.id linked_id, pl.name linked_name FROM tb_projects p left join "fn_GetLinkedProject"(p.id) pl How can I do this? I have read this article. I don't want following method: SELECT p

Select from PostgreSQL function that returns composite type

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How to include a function that returns a composite type in a SELECT ? I have composite type: CREATE TYPE public.dm_nameid AS ( id public.dm_int, name public.dm_str ); Also, I have a function that returns this type fn_GetLinkedProject(integer) . And I need to make something like this: SELECT p.id, p.data, p.name, pl.id linked_id, pl.name linked_name FROM tb_projects p left join "fn_GetLinkedProject"(p.id) pl How can I do this? I have read this article. I don't want following method: SELECT p.id, p.data, p.name, (select pl1.id from "fn_GetLinkedProject"(p.id) pl1 ) linked_id, (select pl2.name

How to read a nested collection in Spark

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问题 I have a parquet table with one of the columns being , array<struct<col1,col2,..colN>> Can run queries against this table in Hive using LATERAL VIEW syntax. How to read this table into an RDD, and more importantly how to filter, map etc this nested collection in Spark? Could not find any references to this in Spark documentation. Thanks in advance for any information! ps. I felt might be helpful to give some stats on the table. Number of columns in main table ~600. Number of rows ~200m.

What is the difference between LATERAL and a subquery in PostgreSQL?

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问题 Since Postgres came out with the ability to do LATERAL joins, I\'ve been reading up on it, since I currently do complex data dumps for my team with lots of inefficient subqueries that make the overall query take four minutes or more. I understand that LATERAL joins may be able to help me, but even after reading articles like this one from Heap Analytics, I still don\'t quite follow. What is the use case for a LATERAL join? What is the difference between a LATERAL join and a subquery? 回答1: