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Transaction isolation levels relation with locks on table
... writes data and commit/rollback (depending on results). B just executes a SELECT statement to read data. C reads and updates data. All these process work on the same table T.
READ UNCOMMITTED - no lock on the table. You can read data in the table while writing on it. This means A writes data (unc...
关于php的socket初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...连接的模型都应该被称为多路复用，目前比较常用的有 select/poll/epoll/kqueue 这些 IO 模型（目前也有像 Apache 这种每个连接用单独的进程/线程来处理的 IO 模型，但是效率相对比较差，也很容易出问题，所以暂时不做介绍了）。在...
Eclipse “Server Locations” section disabled and need to change to use Tomcat installation
...
Here is how I did it:
Right click on my tomcat server in "Servers" view, select "Properties…"
In the "General" panel, click on the "Switch Location" button
The "Location: [workspace metadata]" bit should have been replaced by something else.
Open (or close and reopen) the Overview screen for the...
How to have TFS 2010 detect changes done to files outside of Visual Studio?
...rol Explorer
Right-click on the folder with the changes and choose Compare
Select the files you want to reconcile (press CTRL+A to select all files)
Click on the Reconcile button
Set the options in the Reconcile Folder Differences dialog. Make sure Files that do not have pending changes is set to Ch...
Delete all records in a table of MYSQL in phpMyAdmin
...ampserver 2.2. When I want to delete all records of a table in phpMyAdmin (select all) it deletes only one record not all records. Why it does not delete all records?
...
GROUP_CONCAT ORDER BY
...
You can use ORDER BY inside the GROUP_CONCAT function in this way:
SELECT li.client_id, group_concat(li.percentage ORDER BY li.views ASC) AS views,
group_concat(li.percentage ORDER BY li.percentage ASC)
FROM li GROUP BY client_id
...
Format SQL in SQL Server Management Studio
...ch Visual Studio), and formats the entire script or just the code you have selected/highlighted, if any. Output formatting is customizable.
In SSMS 2008 it combines nicely with the built-in intelli-sense, effectively providing more-or-less the same base functionality as Red Gate's SQL Prompt (SQL P...
PostgreSQL delete with inner join
...ctprice
WHERE m_pricelist_version_id='1000020' AND
m_product_id IN (SELECT m_product_id
FROM m_product
WHERE upc = '7094');
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improve t...
How to export DataTable to Excel
...tring[] columnNames = dataTable.Columns
.Cast<DataColumn>()
.Select(column => column.ColumnName)
.ToArray();
var header = string.Join(",", columnNames.Select(name => $"\"{name}\""));
lines.Add(header);
var valueLines = dataTable.AsEnumerable()
.Select(row => string.J...
Differences between MySQL and SQL Server [closed]
...mplementations.
For example, take a look at the top-n section. In MySQL:
SELECT age
FROM person
ORDER BY age ASC
LIMIT 1 OFFSET 2
In SQL Server (T-SQL):
SELECT TOP 3 WITH TIES *
FROM person
ORDER BY age ASC
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