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What is the dual table in Oracle?
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It's a sort of dummy table with a single record used for selecting when you're not actually interested in the data, but instead want the results of some system function in a select statement:
e.g. select sysdate from dual;
See http://www.adp-gmbh.ch/ora/misc/dual.html
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Regular expression to allow spaces between words
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tl;dr
Just add a space in your character class.
^[a-zA-Z0-9_ ]*$
Now, if you want to be strict...
The above isn't exactly correct. Due to the fact that * means zero or more, it would match all of the following cases that one would not usually mea...
Obtaining a powerset of a set in Java
... return this;
}
}
To call it, use this pattern:
Set<Character> set = new TreeSet<Character> ();
for(int i = 0; i < 5; i++)
set.add((char) (i + 'A'));
PowerSet<Character> pset = new PowerSet<Character>(set);
for(Set&l...
MySQL Orderby a number, Nulls last
...Place a minus sign (-) before the column name and switch the ASC to DESC:
SELECT * FROM tablename WHERE visible=1 ORDER BY -position DESC, id DESC
It is essentially the inverse of position DESC placing the NULL values last but otherwise the same as position ASC.
A good reference is here http://t...
Nested select statement in SQL Server
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You need to alias the subquery.
SELECT name FROM (SELECT name FROM agentinformation) a
or to be more explicit
SELECT a.name FROM (SELECT name FROM agentinformation) a
share
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Keeping it simple and how to do multiple CTE in a query
...s in one query, as well as reuse a CTE:
WITH cte1 AS
(
SELECT 1 AS id
),
cte2 AS
(
SELECT 2 AS id
)
SELECT *
FROM cte1
UNION ALL
SELECT *
FROM cte2
UNION ALL
SELECT *
FROM cte1
Note, however, that SQL Server may reevaluate t...
jQuery or CSS selector to select all IDs that start with some string [duplicate]
How can I select all elements whose id starts with "player_"?
4 Answers
4
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XPath to select Element by attribute value
...he parts in [ ]) shouldn't have slashes immediately before them. Also, to select the Employee element itself, you should leave off the /text() at the end or otherwise you'd just be selecting the whitespace text values immediately under the Employee element.
//Employee[@id='4']
Edit: As Jens poin...
ORACLE 常用日期函数 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
...的日期。如果给出一负数，返回值日期之前几个月日期。select add_months(to_date(&...ADD_MONTHS函数在输入日期上加上指定的几个月返回一个新的日期。如果给出一负数，返回值日期之前几个月日期。
select add_months(to_date('20150201','yyyymmd...
jQuery see if any or no checkboxes are selected
I know how to see if an individual checkbox is selected or not.
8 Answers
8
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