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Is there any difference between GROUP BY and DISTINCT
...CT and distinct by UNION cause an oracle error, but GROUP BY worked; I was selecting only 1 column from a view and not using any aggregation; I'm still baffled why it required it, but it does confirm there is some difference in the execution. As others point out, it also lets you GROUP BY columns no...
Function to Calculate Median in SQL Server
... in all cases. It also requires SQL 2012 or later.
DECLARE @c BIGINT = (SELECT COUNT(*) FROM dbo.EvenRows);
SELECT AVG(1.0 * val)
FROM (
SELECT val FROM dbo.EvenRows
ORDER BY val
OFFSET (@c - 1) / 2 ROWS
FETCH NEXT 1 + (1 - @c % 2) ROWS ONLY
) AS x;
Of course, just because o...
How to select only the first rows for each unique value of a column
...
A very simple answer if you say you don't care which address 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
...
In MySQL, how to copy the content of one table to another table within the same database?
...
INSERT INTO TARGET_TABLE SELECT * FROM SOURCE_TABLE;
EDIT: or if the tables have different structures you can also:
INSERT INTO TARGET_TABLE (`col1`,`col2`) SELECT `col1`,`col2` FROM SOURCE_TABLE;
EDIT: to constrain this..
INSERT INTO TARGET_TAB...
Difference between Select and ConvertAll in C#
...
Select is a LINQ extension method and works on all IEnumerable<T> objects whereas ConvertAll is implemented only by List<T>. The ConvertAll method exists since .NET 2.0 whereas LINQ was introduced with 3.5.
You s...
Can someone explain collection_select to me in clear, simple terms?
I am going through the Rails API docs for collection_select and they are god-awful.
2 Answers
...
How to create a MySQL hierarchical recursive query
... or self-joins.
MySQL 8+
with recursive cte (id, name, parent_id) as (
select id,
name,
parent_id
from products
where parent_id = 19
union all
select p.id,
p.name,
p.parent_id
from products p
inner join cte
...
What's a quick way to comment/uncomment lines in Vim?
...
For those tasks I use most of the time block selection.
Put your cursor on the first # character, press CtrlV (or CtrlQ for gVim), and go down until the last commented line and press x, that will delete all the # characters vertically.
For commenting a block of text i...
How to create a SQL Server function to “join” multiple rows from a subquery into a single delimited
...
If you're using SQL Server 2005, you could use the FOR XML PATH command.
SELECT [VehicleID]
, [Name]
, (STUFF((SELECT CAST(', ' + [City] AS VARCHAR(MAX))
FROM [Location]
WHERE (VehicleID = Vehicle.VehicleID)
FOR XML PATH ('')), 1, 2, '')) AS Locations
FROM [...
How disable Copy, Cut, Select, Select All in UITextView
The UITextView 's Copy, Cut, Select, Select All functionality is shown by default when I press down on the screen. But, in my project the UITextField is only read only. I do not require this functionality. Please tell me how to disable this feature.
...