大约有 9,000 项符合查询结果（耗时：0.0238秒） [XML]
How do I (or can I) SELECT DISTINCT on multiple columns?
... of the currently accepted answer by factor 10 - 15 (in my tests on PostgreSQL 8.4 and 9.1).
But this is still far from optimal. Use a NOT EXISTS (anti-)semi-join for even better performance. EXISTS is standard SQL, has been around forever (at least since PostgreSQL 7.2, long before this question w...
nullable object must have a value
...on methods (e.g. Select, Where), the lambda function might be converted to SQL that might not behave identically to your C# code. For instance, C#'s short-circuit evaluated && and || are converted to SQL's eager AND and OR. This can cause problems when you're checking for null in your lambda...
NoSQL Use Case Scenarios or WHEN to use NoSQL [closed]
...
It really is an "it depends" kinda question. Some general points:
NoSQL is typically good for unstructured/"schemaless" data - usually, you don't need to explicitly define your schema up front and can just include new fields without any ceremony
NoSQL typically favours a denormalised schema d...
.gitignore for Visual Studio Projects and Solutions
....build.csdef
# Windows Store app package directory
AppPackages/
# Others
sql/
*.Cache
ClientBin/
[Ss]tyle[Cc]op.*
~$*
*~
*.dbmdl
*.dbproj.schemaview
*.pfx
*.publishsettings
node_modules/
# RIA/Silverlight projects
Generated_Code/
# Backup & report files from converting an old project file
# ...
Increment value in mysql update query
...
You could also just do this:
mysql_query("
UPDATE member_profile
SET points = points + 1
WHERE user_id = '".$userid."'
");
share
|
improve t...
How to set a default entity property value with Hibernate
...not portable from a database to another, and you need to know the specific SQL language of your server.
– pdem
Sep 20 '16 at 7:30
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Difference between “read commited” and “repeatable read”
...le read simply reads a "snapshot" not the actual data. From the docs dev.mysql.com/doc/refman/5.0/en/…: "All consistent reads within the same transaction read the snapshot established by the first read."
– Derek Litz
Jan 17 '13 at 16:40
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9个常用iptables配置实例 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...时候我们发现某个ip不停的往服务器发包，这时我们可以使用以下命令，将指定ip发来的包丢弃：
BLOCK_THIS_IP="x.x.x.x"
iptables -A INPUT -i eth0 -p tcp -s "$BLOCK_THIS_IP" -j DROP
以上命令设置将由x.x.x.x ip发往eth0网口的tcp包丢弃。
4.配置...
How do I update if exists, insert if not (AKA “upsert” or “merge”) in MySQL?
...RT a row when it does not exist, or to UPDATE if it exists, using one MySQL query?
2 Answers
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Spring JPA @Query with LIKE
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SQL-Injection using your solution possible? (asking because of CONCAT)
– ramden
Nov 8 '18 at 11:22
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