大约有 41,000 项符合查询结果（耗时：0.0340秒） [XML]
Difference between natural join and inner join
...+----------+
The INNER JOIN of TableA and TableB on Column1 will return
SELECT * FROM TableA AS a INNER JOIN TableB AS b USING (Column1);
SELECT * FROM TableA AS a INNER JOIN TableB AS b ON a.Column1 = b.Column1;
+------------+-----------+---------------------+
| a.Column1 | a.Column2 | ...
Select objects based on value of variable in object using jq
...
Adapted from this post on Processing JSON with jq, you can use the select(bool) like this:
$ jq '.[] | select(.location=="Stockholm")' json
{
"location": "Stockholm",
"name": "Walt"
}
{
"location": "Stockholm",
"name": "Donald"
}
...
Get top 1 row of each group
...
;WITH cte AS
(
SELECT *,
ROW_NUMBER() OVER (PARTITION BY DocumentID ORDER BY DateCreated DESC) AS rn
FROM DocumentStatusLogs
)
SELECT *
FROM cte
WHERE rn = 1
If you expect 2 entries per day, then this will arbitrarily pick one...
Linq Syntax - Selecting multiple columns
...
.Where(x => x.EMAIL == givenInfo || x.USER_NAME == givenInfo)
.Select(x => new { x.EMAIL, x.ID });
AFAIK, the declarative LINQ syntax is converted to a method call chain similar to this when it is compiled.
UPDATE
If you want the entire object, then you just have to omit the call ...
Iterate through options
I have a <select> element in HTML. This element represents a drop down list. I'm trying to understand how to iterate through the options in the <select> element via JQuery.
...
How to do INSERT into a table records extracted from another table
...UES", no parenthesis:
INSERT INTO Table2(LongIntColumn2, CurrencyColumn2)
SELECT LongIntColumn1, Avg(CurrencyColumn) as CurrencyColumn1 FROM Table1 GROUP BY LongIntColumn1;
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SQL Server: Examples of PIVOTing String data
...l as numbers. This query will only require the table to be scanned once.
SELECT Action,
MAX( CASE data WHEN 'View' THEN data ELSE '' END ) ViewCol,
MAX( CASE data WHEN 'Edit' THEN data ELSE '' END ) EditCol
FROM t
GROUP BY Action
...
Measure the time it takes to execute a t-sql query
... to just grab the current date and time.
In SQL Server Management Studio
SELECT GETDATE();
SELECT /* query one */ 1 ;
SELECT GETDATE();
SELECT /* query two */ 2 ;
SELECT GETDATE();
To calculate elapsed times, you could grab those date values into variables, and use the DATEDIFF function:
DECL...
How to map and remove nil values in Ruby
...blem:
N = 1_00_000
enum = 1.upto(1_000)
Benchmark.bmbm do |x|
x.report("select + map") { N.times { enum.select { |i| i.even? }.map{|i| i + 1} } }
x.report("map + compact") { N.times { enum.map { |i| i + 1 if i.even? }.compact } }
x.report("filter_map") { N.times { enum.filter_map { |i| i ...
Get top n records for each group of grouped results
...ould need to specify the group number and add queries for each group:
(
select *
from mytable
where `group` = 1
order by age desc
LIMIT 2
)
UNION ALL
(
select *
from mytable
where `group` = 2
order by age desc
LIMIT 2
)
There are a variety of ways to do this, see this articl...