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How to select only the first rows for each unique value of a column
...ddress is used.
SELECT
CName, MIN(AddressLine)
FROM
MyTable
GROUP BY
CName
If you want the first according to, say, an "inserted" column then it's a different query
SELECT
M.CName, M.AddressLine,
FROM
(
SELECT
CName, MIN(Inserted) AS First
FROM
MyTable...
mysql error 1364 Field doesn't have a default values
...
Set a default value for Created_By (eg: empty VARCHAR) and the trigger will update the value anyways.
create table try (
name varchar(8),
CREATED_BY varchar(40) DEFAULT '' not null
);
...
How does PHP 'foreach' actually work?
Let me prefix this by saying that I know what foreach is, does and how to use it. This question concerns how it works under the bonnet, and I don't want any answers along the lines of "this is how you loop an array with foreach ".
...
PostgreSQL Crosstab Query
...
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 | Inactive
---------+--------+----------
A | 1 | 2
B | 4 | ...
Applying a function to every row of a table using dplyr?
...
You need to group by row:
iris %>% group_by(1:n()) %>% mutate(Max.Len= max(Sepal.Length,Petal.Length))
This is what the 1 did in adply.
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What is meant by the term “hook” in programming?
...ay be able to hook into the interrupt handling process though, for example by modifiying the table listing the locations of the interrupt handlers so that your code gets called first on interrupt (and then your code would call the previously present interrupt handling code, in a daisy-chain manner)
...
What is the difference between HAVING and WHERE in SQL?
...his code:
select City, CNT=Count(1)
From Address
Where State = 'MA'
Group By City
Gives you a table of all cities in MA and the number of addresses in each city.
This code:
select City, CNT=Count(1)
From Address
Where State = 'MA'
Group By City
Having Count(1)>5
Gives you a table of cities...
How to define a custom ORDER BY order in mySQL
...ndy function called FIELD() which is excellent for tasks like this.
ORDER BY FIELD(Language,'ENU','JPN','DAN'), ID
Note however, that
It makes your SQL less portable, as other DBMSs might not have such function
When your list of languages (or other values to sort by) gets much longer, it's bette...
Clear text from textarea with selenium
...
driver.find_element_by_id('foo').clear()
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Grouping functions (tapply, by, aggregate) and the *apply family
...er answers) that much of the functionality of the *apply family is covered by the extremely popular plyr package, the base functions remain useful and worth knowing.
This answer is intended to act as a sort of signpost for new useRs to help direct them to the correct *apply function for their parti...