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How to open existing project in Eclipse
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Project > Import > General > Select Root Directory > (do NOT select copy projects into workspace). This is useful if you use Eclipse outside scope of Java project as well, such as Ruby projects or C projects.
– JohnMerlino
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How to check if field is null or empty in MySQL?
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Either use
SELECT IF(field1 IS NULL or field1 = '', 'empty', field1) as field1
from tablename
or
SELECT case when field1 IS NULL or field1 = ''
then 'empty'
else field1
end as field1
from tablename
...
Condition within JOIN or WHERE
...of filtering criteria more easily maintainable.
For example, instead of:
SELECT *
FROM Customers c
INNER JOIN CustomerAccounts ca
ON ca.CustomerID = c.CustomerID
AND c.State = 'NY'
INNER JOIN Accounts a
ON ca.AccountID = a.AccountID
AND a.Status = 1
Write:
SELECT *
FROM Customer...
How do I write LINQ's .Skip(1000).Take(100) in pure SQL?
...W_NUMBER function. eg.
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 51 AND 60; --BETWEEN is inclusive
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How can I resolve “Error: No developer directory found at /Developer”?
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sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer
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Postgresql aggregate array
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Use array_agg: http://www.sqlfiddle.com/#!1/5099e/1
SELECT s.name, array_agg(g.Mark) as marks
FROM student s
LEFT JOIN Grade g ON g.Student_id = s.Id
GROUP BY s.Id
By the way, if you are using Postgres 9.1, you don't need to repeat the columns on SELECT to GROUP BY,...
Android系统级推送原理详解：为什么App被杀也能收到通知？ - App应用开发 -...
本文是"App Inventor 2 推送通知调研"系列的第三篇
相关帖子：AI2能否实现后台推送？源码级深度调研 | Supabase扩展Realtime能力分析
很多开发者都好奇：微信、淘宝这些 App，明明已经被我从后台杀掉了，为什么还能收到...
Warning as error - How to rid these
...h of your projects and change that setting:
Right-click on your project, select "Properties".
Click "Build".
Switch "Treat warnings as errors" from "All" to "Specific warnings" or "None".
The location of this switch varies, depending on the type of project (class library vs. web application, for...
Are there any disadvantages to always using nvarchar(MAX)?
...E @SomeString NVARCHAR(10),
@StartTime DATETIME;
--=====
SELECT @startTime = GETDATE();
SELECT TOP 1000000
@SomeString = 'ABC'
FROM master.sys.all_columns ac1,
master.sys.all_columns ac2;
SELECT testTime='10', Duration = DATEDIFF(ms,@StartTime,GETDATE());
GO
--...
Python Pandas: Get index of rows which column matches certain value
... [57]: idx
Out[57]: Int64Index([10, 40, 50], dtype='int64')
then you can select the rows using loc instead of iloc:
In [58]: df.loc[idx]
Out[58]:
BoolCol
10 True
40 True
50 True
[3 rows x 1 columns]
Note that loc can also accept boolean arrays:
In [55]: df.loc[df['BoolCol']]
Ou...