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MySQL ON vs USING?
...n tables ON a column, a set of columns and even a condition. For example:
SELECT * FROM world.City JOIN world.Country ON (City.CountryCode = Country.Code) WHERE ...
USING is useful when both tables share a column of the exact same name on which they join. In this case, one may say:
SELECT ... FR...
How to submit form on change of dropdown list?
I am creating a page in JSP where I have a dropdown list and once the user selects a value he has to click on the go button and then the value is sent to the Servlet.
...
How can I select rows with most recent timestamp for each key value?
...r data. Each row has a sensor id, a timestamp, and other fields. I want to select a single row with latest timestamp for each sensor, including some of the other fields.
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How can I select the first day of a month in SQL?
I just need to select the first day of the month of a given datetime variable.
30 Answers
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PostgreSQL Crosstab Query
... - not fit for missing attributes
crosstab(text) with 1 input parameter:
SELECT *
FROM crosstab(
'SELECT section, status, ct
FROM tbl
ORDER BY 1,2' -- needs to be "ORDER BY 1,2" here
) AS ct ("Section" text, "Active" int, "Inactive" int);
Returns:
Section | Active | Inacti...
How to get the selected index of a RadioGroup in Android
Is there an easy way to get the selected index of a RadioGroup in Android or do I have to use OnCheckedChangeListener to listen for changes and have something that holds the last index selected?
...
How to compute the similarity between two text documents?
...
with 17 stored elements in Compressed Sparse Row format>
You can convert the sparse array to a NumPy array via .toarray() or .A:
>>> pairwise_similarity.toarray() ...
Get Base64 encode file-data from Input Form
...a or doing other voodoo magic before you upload.
There are two methods:
Convert to string and use the built-in btoa or similar
I haven't tested all cases, but works for me- just get the char-codes
Convert directly from a Uint8Array to base64
I recently implemented tar in the browser. As par...
jQuery count child elements
...
You can use .length with just a descendant selector, like this:
var count = $("#selected li").length;
If you have to use .children(), then it's like this:
var count = $("#selected ul").children().length;
You can test both versions here.
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MySQL: Fastest way to count number of rows
...s.
The solution is SQL_CALC_FOUND_ROWS. This is usually used when you are selecting rows but still need to know the total row count (for example, for paging).
When you select data rows, just append the SQL_CALC_FOUND_ROWS keyword after SELECT:
SELECT SQL_CALC_FOUND_ROWS [needed fields or *] FROM t...