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MySQL how to join tables on two fields
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SELECT *
FROM t1
JOIN t2 USING (id, date)
perhaps you'll need to use INNEER JOIN or
where t2.id is not null
if you want results only matching both conditions
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Debugging sqlite database on the device
...ed a database with two tables and a dozen or so rows in each, and did full select queries on each table. One worked fine, the other reported a data error in the file. My best guess right now is an encoding mismatch between the Android and local shell.
– Mason
F...
Bash command to sum a column of numbers [duplicate]
... With bc -l you can even add up float numbers. With cut you can select columns from the input: cat input.txt | cut -d ' ' -f 8 | paste -sd+ | bc -l will add all float numbers in column 8 of the input (space being the field separator).
– Arne
Sep 24 '...
Using .gitignore to ignore everything but specific directories
...at I have a bunch of WordPress websites in my git repo, of which I want to selectively commit only the content of my themes folders, while ignoring the rest of the redundant files found in WordPress.
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Converting many 'if else' statements to a cleaner approach [duplicate]
...s not what you need here, this isn't modelling a finite state machine it's selecting a different conversion strategy based on the input type so the strategy pattern is more appropriate.
– Paolo
Jan 3 '13 at 13:55
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jQuery hasAttr checking to see if there is an attribute on an element [duplicate]
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What about api.jquery.com/has-attribute-selector
– Aamir Afridi
Jan 30 '13 at 14:19
3
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How to write a simple database engine [closed]
...h pattern of delimiter is never used in your data itself. i.e. if you have selected <*> for example to separate columns, you should validate the data you are placing in this table not to contain this pattern. you could also use a row header and a column header by specifying size of row and som...
Rails: How to change the title of a page?
...In rails 3 content_for is smart enough to work correctly with caching (see selected answer).
– opsb
Nov 15 '11 at 10:41
4
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pandas: filter rows of DataFrame with operator chaining
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Since version 0.18.1 the .loc method accepts a callable for selection. Together with lambda functions you can create very flexible chainable filters:
import numpy as np
import pandas as pd
df = pd.DataFrame(np.random.randint(0,100,size=(100, 4)), columns=list('ABCD'))
df.loc[lambda ...
ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
... table. Following query would be helpful to fetch those non-matching rows:
SELECT child_table.*
FROM child_table
LEFT JOIN parent_table
ON parent_table.referenced_column = child_table.referencing_column
WHERE parent_table.referenced_column IS NULL
Now, you can generally do one (or more) of th...