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Multiple columns index when using the declarative ORM extension of sqlalchemy
According to the documentation and the comments in the sqlalchemy.Column class, we should use the class sqlalchemy.schema.Index to specify an index that contains multiple columns.
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Python assigning multiple variables to same value? list behavior
I tried to use multiple assignment as show below to initialize variables, but I got confused by the behavior, I expect to reassign the values list separately, I mean b[0] and c[0] equal 0 as before.
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Check if object value exists within a Javascript array of objects and if not add a new object to arr
If I have the following array of objects:
18 Answers
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In Flux architecture, how do you manage Store lifecycle?
I'm reading about Flux but the example Todo app is too simplistic for me to understand some key points.
3 Answers
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Update multiple rows in same query using PostgreSQL
I'm looking to update multiple rows in PostgreSQL in one statement. Is there a way to do something like the following?
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How to delete duplicates on a MySQL table?
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this removes duplicates in place, without making a new table
ALTER IGNORE TABLE `table_name` ADD UNIQUE (title, SID)
note: only works well if index fits in memory
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What is the difference between partitioning and bucketing a table in Hive ?
I know both is performed on a column in the table but how is each operation different.
8 Answers
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MySQL ON vs USING?
In a MySQL JOIN , what is the difference between ON and USING() ? As far as I can tell, USING() is just more convenient syntax, whereas ON allows a little more flexibility when the column names are not identical. However, that difference is so minor, you'd think they'd just do away with USI...
Avoid duplicates in INSERT INTO SELECT query in SQL Server
I have the following two tables:
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How do I get a list of all the duplicate items using pandas in python?
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Method #1: print all rows where the ID is one of the IDs in duplicated:
>>> import pandas as pd
>>> df = pd.read_csv("dup.csv")
>>> ids = df["ID"]
>>> df[ids.isin(ids[ids.duplicated()])].sort("ID")
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