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SQL JOIN vs IN performance?
... faster more often than not.
So if you are only interested in values from table a you can use this query:
SELECT a.*
FROM a
WHERE EXISTS (
SELECT *
FROM b
WHERE b.col = a.col
)
The difference might be huge if col is not indexed, because the db does not have to find al...
Dump a mysql database to a plaintext (CSV) backup from the command line
...only convenient for mysql to read. CSV seems more universal (one file per table is fine). But if there are advantages to mysqldump, I'm all ears. Also, I'd like something I can run from the command line (linux). If that's a mysql script, pointers to how to make such a thing would be helpful.
...
Child inside parent with min-height: 100% not inheriting height
...
Second, the workaround I found:
If I set my container element to display:table with height:inherit it acts exactly the same way as if I'd give it a min-height of 100%. And - more importantly - if I set the child element to display:table-cell it will perfectly inherit the height of the container el...
What are the most common SQL anti-patterns? [closed]
... will do.
DECLARE @LoopVar int
SET @LoopVar = (SELECT MIN(TheKey) FROM TheTable)
WHILE @LoopVar is not null
BEGIN
-- Do Stuff with current value of @LoopVar
...
--Ok, done, now get the next value
SET @LoopVar = (SELECT MIN(TheKey) FROM TheTable
WHERE @LoopVar < TheKey)
END
Number 3....
Remove duplicated rows
...
The data.table package also has unique and duplicated methods of it's own with some additional features.
Both the unique.data.table and the duplicated.data.table methods have an additional by argument which allows you to pass a chara...
Difference between 3NF and BCNF in simple terms (must be able to explain to an 8-year old)
...hree topping types:
one type of cheese
one type of meat
one type of vegetable
So we order two pizzas and choose the following toppings:
Pizza Topping Topping Type
-------- ---------- -------------
1 mozzarella cheese
1 pepperoni meat
1 olives vegetable
2 ...
How to create a responsive image that also scales up in Bootstrap 3
...option, here's an alternative solution.
Having a parent div with display: table & table-layout: fixed.
Then setting the image to display: table-cell and max-width to 100%. That way the image will fit to the width of its parent.
Example:
<style>
.wrapper { float: left; clear: left; d...
Bring element to front using CSS
...28px;
}
.content {
margin-left: auto;
margin-right: auto;
table-layout: fixed;
border-collapse: collapse;
z-index: -1;
position:relative;
}
.td-main {
text-align: center;
padding: 80px 10px 80px 10px;
border: 1px solid #A02422;
background: #ABABA...
Frequency table for a single variable
One last newbie pandas question for the day: How do I generate a table for a single Series?
4 Answers
...
SQL query to group by day
...
If you're using SQL Server, you could add three calculated fields to your table:
Sales (saleID INT, amount INT, created DATETIME)
ALTER TABLE dbo.Sales
ADD SaleYear AS YEAR(Created) PERSISTED
ALTER TABLE dbo.Sales
ADD SaleMonth AS MONTH(Created) PERSISTED
ALTER TABLE dbo.Sales
ADD SaleDay A...