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Questions - left-join

Merging two different dataframes

I'm having an issue merging two different data frames based on column names. Code: import os, json, xlsxwriter import pandas as pd left = pd.DataFrame({'CompID': ['Computer-8', 'Computer-D', 'Compute...
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Ali987

python

pandas

dataframe

join

left-join

Votes: 0

Answers: 1

Latest Answer

In a simplistic way, you can do the following: First create the merged dataframes. new_df = pd.merge(left, right, how='left', left_on=['WindowsOsVersion'], right_on = ['OsName']) new_df = pd.merge(ne...
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alkes

Joining 2 Select Queries (one query including an aggregate function) from two different tables

I am trying to left join the two queries below (mock data for reference purposes). SELECT marker_number AS ISN, IF(shelf_life_code = 'A', 1, 0) AS Store_Repaired, SUBSTRING(marker_number, ...
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PythonLearner

sql

left-join

aggregate-functions

databricks

Votes: 0

Answers: 1

Latest Answer

With A as(SELECT marker_number AS ISN, IF(shelf_life_code = 'A', 1, 0) AS Store_Repaired, SUBSTRING(marker_number, 5, 9) AS item_number_id, IF(action_code = '1',1,0) AS Transferred...
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Diganta Dey

LEFT JOIN limited number of rows with GROUP_CONCAT too slow

I boiled the question down in the db fiddle below. I have an object table and an images table. X images can be assigned to an object. Now I have a list where a configurable amount of images needs to b...
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Mike

mysql

left-join

group-concat

Votes: 0

Answers: 3

Latest Answer

The first thing I notice in your dbfiddle is that you have no index on images(oid), so your condition in your subquery is doing a table-scan of the images table. That could be a part of the performanc...
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Bill Karwin

How to use columns from the left table in where clause in the right select statement in SQL Server join statement

I want to join a table with the output of select statement where I need to use a column last_order_date from Table1 in the WHERE clause in the select statement. For example, see this screenshot: I tr...
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Abdullah Bahi

sql

sql-server

left-join

Votes: 0

Answers: 1

Latest Answer

You can try to use OUTER APPLY SELECT * FROM Table1 t1 OUTER APPLY ( SELECT t2.prod_id, SUM(t2.sales) sales_sum FROM Table2 t2 WHERE t2.transaction_date BETWEEN t1.last_order_date...
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D-Shih

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