大约有 47,000 项符合查询结果（耗时：0.0420秒） [XML]
JPA eager fetch does not join
...
JPA doesn't provide any specification on mapping annotations to select fetch strategy. In general, related entities can be fetched in any one of the ways given below
SELECT => one query for root entities + one query for related mapped entity/collection of each root entity = (n+1) que...
postgresql COUNT(DISTINCT …) very slow
...
You can use this:
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
This is much faster than:
COUNT(DISTINCT column_name)
share
...
Return empty cell from formula in Excel
...a by changing SomeRange to Range("MyRange"). To set a name for your cells, select the cells, click Define Name on the Formulas tab of the ribbon, and enter "MyRange" in the Name field. (And of course you could replace MyRange with anything you want.)
– devuxer
...
How can I return pivot table output in MySQL?
...OUP BY.
The basic SQL providing this pivot can look something like this:
SELECT P.`company_name`,
COUNT(
CASE
WHEN P.`action`='EMAIL'
THEN 1
ELSE NULL
END
) AS 'EMAIL',
COUNT(
CASE
WHEN P.`action`='PRINT' AND...
How do I get a distinct, ordered list of names from a DataTable using LINQ?
...tainable, you can also split it up into multiple LINQ statements.
First, select your data into a new list, let's call it x1, do a projection if desired
Next, create a distinct list, from x1 into x2, using whatever distinction you require
Finally, create an ordered list, from x2 into x3, sorting by...
How to set timeout on python's socket recv method?
...
The typical approach is to use select() to wait until data is available or until the timeout occurs. Only call recv() when data is actually available. To be safe, we also set the socket to non-blocking mode to guarantee that recv() will never block indef...
Which timestamp type should I choose in a PostgreSQL database?
...al time zone
test=> SET timezone = 'America/Los_Angeles';
SET
test=> SELECT NOW();
now
-------------------------------
2011-05-27 15:47:58.138995-07
(1 row)
test=> SELECT NOW() AT TIME ZONE 'UTC';
timezone
----------------------------
2011-...
Map and Reduce in .NET
...ons. C# 3.5 and Linq already has it albeit under different names.
Map is Select:
Enumerable.Range(1, 10).Select(x => x + 2);
Reduce is Aggregate:
Enumerable.Range(1, 10).Aggregate(0, (acc, x) => acc + x);
Filter is Where:
Enumerable.Range(1, 10).Where(x => x % 2 == 0);
https://www...
Getting attribute using XPath
...e), for
the first element?
Use:
/*/book[1]/title/@lang
This means:
Select the lang attribute of the title element that is a child of the first book child of the top element of the XML document.
To get just the string value of this attribute use the standard XPath function string():
string(...
Eclipse doesn't highlight references anymore
... If none of comments above worked, uncheck "Mark occurrences of the selected element in the current file" > Apply > OK. Go back to preferences, check "Mark occurrences of the selected element in the current file" > Apply > OK.
– realPK
Feb 4 ...