大约有 40,000 项符合查询结果（耗时：0.0453秒） [XML]
What does it mean by select 1 from table?
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SELECT 1 FROM TABLE_NAME means, "Return 1 from the table". It is pretty unremarkable on its own, so normally it will be used with WHERE and often EXISTS (as @gbn notes, this is not necessarily best practice, it is, however, c...
Where are my postgres *.conf files?
...alives_idle = 0 # TCP_KEEPIDLE, in seconds;
# 0 selects the system default
#tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds;
# 0 selects the system default
#tcp_keepalives_count = 0 # TCP_KEEPCNT;
# 0 selects the...
Difference between “change” and “input” event for an `input` element
...an element is changed through the user interface.
onchange occurs when the selection, the checked state or the contents of an element have changed. In some cases, it only occurs when the element loses the focus or when pressing return (Enter) and the value has been changed. The onchange attribute ca...
How to create relationships in MySQL
...s defined as the default storage engine,can check using command (mysql> SELECT @@default_storage_engine;)
– Arun
Feb 18 at 4:00
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MyISAM versus InnoDB [closed]
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Frequent select queries Yes
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Frequent insert, update, delete Yes
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Faster way to develop and test print stylesheets (avoid print preview every time)?
...P (Mac) or Ctrl+Shift+P (Windows, Linux))
2. Start typing Rendering and select Show Rendering.
3. For the Emulate CSS Media dropdown, select print.
UPDATE 29/02/2016
The DevTools docs have moved and the above link provides inaccurate information. The updated docs regarding Media type em...
SQL Server 2012 column identity increment jumping from 6 to 1000+ on 7th entry [duplicate]
...TrackerMessageId INT
DECLARE @intRowCount INT
SET @intRowCount = (SELECT COUNT(*) FROM INSERTED)
SET @intTrackerMessageId = (SELECT intIdentityLast FROM tblsysIdentities WHERE intTableId=1)
UPDATE tblsysIdentities SET intIdentityLast = @intTrackerMessageId + @intRowCount WHERE intT...
Data structure: insert, remove, contains, get random element, all at O(1)
...o other solutions).
The requirement that's tricky is the "random element" selection: in a hash table, you would need to scan or probe for such an element.
For closed hashing / open addressing, the chance of any given bucket being occupied is size() / capacity(), but crucially this is typically kep...
Why can't I reference System.ComponentModel.DataAnnotations?
...odel.DataAnnotations assembly (Solution explorer -> Add reference -> Select .Net tab -> select System.ComponentModel.DataAnnotations from the list)
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What's the Point of Multiple Redis Databases?
...e instances lets you take advantage of multiple cores. If you use database selection you will have to refactor when upgrading. Monitoring and managing multiple instances is not difficult nor painful.
Indeed, you would get far better metrics on each db by segregation based on instance. Each instanc...