大约有 41,000 项符合查询结果（耗时：0.0453秒） [XML]
DISTINCT for only one column
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If you are using SQL Server 2005 or above use this:
SELECT *
FROM (
SELECT ID,
Email,
ProductName,
ProductModel,
ROW_NUMBER() OVER(PARTITION BY Email ORDER BY ...
Fast way to discover the row count of a table in PostgreSQL
...in your case.
Instead of getting the exact count (slow with big tables):
SELECT count(*) AS exact_count FROM myschema.mytable;
You get a close estimate like this (extremely fast):
SELECT reltuples::bigint AS estimate FROM pg_class where relname='mytable';
How close the estimate is depends on ...
Call PowerShell script PS1 from another PS1 script inside Powershell ISE
...bind argument to parameter 'Path' because it is an empty string. At line:4 char:25 + $ScriptPath = Split-Path <<<< $MyInvocation.InvocationName + CategoryInfo : InvalidData: (:) [Split-Path], ParameterBindingValidationException + FullyQualifiedErrorId : ParameterArgumen...
Java: Clear the console
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System.out.println(new String(new char[50]).replace("\0", "\r\n")); will do the job faster and better.
– Aaron Esau
Dec 30 '17 at 0:28
1
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MySQL: Insert record if not exists in table
...oDB;
Insert a record:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
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How do I change selected value of select2 dropdown with JqGrid?
I'm using Oleg's select2 demo , but I am wondering whether it would be possible to change the currently selected value in the dropdown menu.
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PostgreSQL return result set as JSON array?
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TL;DR
SELECT json_agg(t) FROM t
for a JSON array of objects, and
SELECT
json_build_object(
'a', json_agg(t.a),
'b', json_agg(t.b)
)
FROM t
for a JSON object of arrays.
List of objects
This section de...
What are these ^M's that keep showing up in my files in emacs?
...file, but it still let me 'git clone code.google.com/p/pytomtom' with '^m' chars?????
– Big Rich
Mar 17 '15 at 12:26
12
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Fastest method to escape HTML tags as HTML entities?
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In normal text escaped characters are rare. It's better to call replace only when needed, if you care about max speed: if (/[<>&"]/.test(str) { ... }
– Vitaly
Oct 26 '14 at 4:22
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How to use OpenFileDialog to select a folder?
How to use OpenFileDialog to select folders?
8 Answers
8
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