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Group query results by month and year in postgresql
...ht make sense to use date_trunc, but in some cases having a formatted date string is preferable, and if you're using a performant data warehouse the additional computation might not be a deal breaker. For example, if you are running a quick analytics report using redshift, and it usually takes 3 sec...
Please explain the exec() function and its family
... family have different behaviours:
l : arguments are passed as a list of strings to the main()
v : arguments are passed as an array of strings to the main()
p : path/s to search for the new running program
e : the environment can be specified by the caller
You can mix them, therefore you have:
...
How to persist a property of type List in JPA?
... should anyone be looking for an alternative solution where you store your string lists as one field in your database, here's how I solved that. Create a Converter like this:
import java.util.Arrays;
import java.util.List;
import javax.persistence.AttributeConverter;
import javax.persistence.Conve...
psql: FATAL: Peer authentication failed for user “dev”
...0.0.1 -d db_name
where
-U is the database user name
-h is the hostname/IP of the local server, thus avoiding Unix domain sockets
-d is the database name to connect to
This is then evaluated as a "network" connection by Postgresql rather than a Unix domain socket connection, thus not evaluated ...
How to convert DateTime to VarChar
...DECLARE @myDateTime DATETIME
SET @myDateTime = '2008-05-03'
--
-- Convert string
--
SELECT LEFT(CONVERT(VARCHAR, @myDateTime, 120), 10)
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How to find memory leak in a C++ code/project?
...you allocated:
char* str = new char [30]; // Allocate 30 bytes to house a string.
delete [] str; // Clear those 30 bytes and make str point nowhere.
2
Reallocate memory only if you've deleted. In the code below, str acquires a new address with the second allocation. The first address is lost ir...
MongoDB数据导出导入工具：mongoexport,mongoimport - 大数据 & AI - 清泛...
...ds names - 1 per line
-q [ --query ] arg query filter, as a JSON string
--csv export to csv instead of json
-o [ --out ] arg output file; if not specified, stdout is used
--jsonArray output to a json array rather than one object per
...
Fastest way to remove first char in a String
Say we have the following string
4 Answers
4
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CruiseControl.Net 进行持续化集成 - IT产品资讯 - 清泛网 - 专注C/C++及内核技术
...
Visual Studio SouceSafe
本局域网下一台服务器,IP地址192.168.1.200,共享目录:VSS,所以其根路径为: \\192.168.1.200\\VSS ,用户名user,密码pwd
CC.Net
CC.Net安装在IP地址为:192.168.1.10的服务器上。
单元测试工...
Is there an auto increment in sqlite?
...ect (bold & italic are mine):
The AUTOINCREMENT keyword imposes extra CPU, memory, disk space, and
disk I/O overhead and should be avoided if not strictly needed. It is
usually not needed.
In SQLite, a column with type INTEGER PRIMARY KEY is an alias for the
ROWID (except in WITHO...