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How can i use iptables on centos 7? [closed]
... trying to open 80 port for httpd service, but something wrong with my iptables service ... what's wrong with it? What am I doing wrong?
...
Why there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT clause?
...012-04-10, Milestone 8)
Previously, at most one TIMESTAMP column per table could be
automatically initialized or updated to the current date and time.
This restriction has been lifted. Any TIMESTAMP column definition can
have any combination of DEFAULT CURRENT_TIMESTAMP and ON UPDATE
C...
What is the “owning side” in an ORM mapping?
... example of two entities mapped without declaring a owning side:
@Entity
@Table(name="PERSONS")
public class Person {
@OneToMany
private List<IdDocument> idDocuments;
}
@Entity
@Table(name="ID_DOCUMENTS")
public class IdDocument {
@ManyToOne
private Person person;
}
From a...
How are virtual functions and vtable implemented?
...ons in C++":
Whenever a program has a virtual function declared, a v - table is constructed for the class. The v-table consists of addresses to the virtual functions for classes that contain one or more virtual functions. The object of the class containing the virtual function contains a virtual...
How to import multiple .csv files at once?
...r answers using things like do.call(rbind,...), dplyr::bind_rows() or data.table::rbindlist().
If you really want each data frame in a separate object, even though that's often inadvisable, you could do the following with assign:
temp = list.files(pattern="*.csv")
for (i in 1:length(temp)) assign(...
How do I get SUM function in MySQL to return '0' if no values are found?
...Use COALESCE to avoid that outcome.
SELECT COALESCE(SUM(column),0)
FROM table
WHERE ...
To see it in action, please see this sql fiddle: http://www.sqlfiddle.com/#!2/d1542/3/0
More Information:
Given three tables (one with all numbers, one with all nulls, and one with a mixture):
SQL Fidd...
How To Change DataType of a DataColumn in a DataTable?
...
You cannot change the DataType after the Datatable is filled with data. However, you can clone the Data table, change the column type and load data from previous data table to the cloned table as shown below.
DataTable dtCloned = dt.Clone();
dtCloned.Columns[0].DataTyp...
Export Postgresql table data using pgAdmin
...
Just right click on a table and select "backup". The popup will show various options, including "Format", select "plain" and you get plain SQL.
pgAdmin is just using pg_dump to create the dump, also when you want plain SQL.
It uses something lik...
Lua简明教程 - 脚本技术 - 清泛IT论坛，有思想、有深度
...unction foo(x) return x^2 end
foo = function(x) return x^2 end复制代码
Table所谓Table其实就是一个Key Value的数据结构，它很像Javascript中的Object，或是PHP中的数组，在别的语言里叫Dict或Map，Table长成这个样子：haoel = {name="ChenHao", age=37, han...
Is it possible to use the SELECT INTO clause with UNION [ALL]?
In SQL Server this inserts 100 records, from the Customers table into tmpFerdeen :-
8 Answers
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