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How to 'insert if not exists' in MySQL?
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Solution:
INSERT INTO `table` (`value1`, `value2`)
SELECT 'stuff for value1', 'stuff for value2' FROM DUAL
WHERE NOT EXISTS (SELECT * FROM `table`
WHERE `value1`='stuff for value1' AND `value2`='stuff for value2' LIMIT 1)
Explanation:
The innermost query
SELECT *...
How to get last N records with activerecord?
...e-wise - at least not up to Rails 3.1. SomeModel.last(5) will execute the select statement without a limit, returning all records of SomeModel to Ruby as an array, after which Ruby will pick out the last (5) elements. Efficiency-wise, currently, you want to use limit - particularly if you have pote...
Create an Android Jar library for distribution
...ormal Java project in Eclipse, add the android.jar to the build path, then select Export - Java - Jar File.
– Jeff Gilfelt
Feb 16 '11 at 10:47
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jQuery: select an element's class and id at the same time?
I've got some links that I want to select class and id at the same time.
6 Answers
6
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Mysql: Select rows from a table that are not in another
How to select all rows in one table that do not appear on another?
8 Answers
8
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Freezing Row 1 and Column A at the same time
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Select cell B2 and click "Freeze Panes" this will freeze Row 1 and Column A.
For future reference, selecting Freeze Panes in Excel will freeze the rows above your selected cell and the columns to the left of your selected ce...
Select Pandas rows based on list index
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For large datasets, it is memory efficient to read only selected rows via the skiprows parameter.
Example
pred = lambda x: x not in [1, 3]
pd.read_csv("data.csv", skiprows=pred, index_col=0, names=...)
This will now return a DataFrame from a file that skips all rows except 1 and ...
How do I get SUM function in MySQL to return '0' if no values are found?
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Use COALESCE to avoid that outcome.
SELECT COALESCE(SUM(column),0)
FROM table
WHERE ...
To see it in action, please see this sql fiddle: http://www.sqlfiddle.com/#!2/d1542/3/0
More Information:
Given three tables (one with all numbers, one with all nul...
JUnit 4 Test Suites
...lipse:
In the 'Package Explorer' view of the eclipse 'Java' perspective,
select your unit test(s) in their package, inside the eclipse java
project.
Right-click on any one of the selected tests.
In the pop-up menu, select New, Other…
Open the ‘Java’ folder, then open the ‘JUnit’ folder...
CSS3 selector :first-of-type with class name?
Is it possible to use the CSS3 selector :first-of-type to select the first element with a given class name? I haven't been successful with my test so I'm thinking it's not?
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