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Which is faster/best? SELECT * or SELECT column1, colum2, column3, etc
... that SQL Server can access the data from indexes rather than querying the table data.
Here's a post I wrote about it: The real reason select queries are bad index coverage
It's also less fragile to change, since any code that consumes the data will be getting the same data structure regardless...
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...
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
...
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...
MySQL - SELECT WHERE field IN (subquery) - Extremely slow why?
...
Rewrite the query into this
SELECT st1.*, st2.relevant_field FROM sometable st1
INNER JOIN sometable st2 ON (st1.relevant_field = st2.relevant_field)
GROUP BY st1.id /* list a unique sometable field here*/
HAVING COUNT(*) > 1
I think st2.relevant_field must be in the select, because other...
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...
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...
generate model using user:references vs user_id:integer
...
Is it possible to generate a model with references of two tables
– praveenkumar
Dec 8 '16 at 6:41
Not...
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...