Stop Using for…in Loop Statement to Iterate Array In JavaScript

for…in loop statement is working fine. The problem is it does not work with Prototype. So standard loop statement is encouraged:

; for (var index=0; index { ; var item = myArray[index]
// Your code working on item here...
}

In addition, if the array is so large, each time to check the length will be so costly. Use following statement instead:

; for (var index=0, len=myArray.length; index { ; var item = myArray[index]
// Your code working on item here...
}


http://www.prototypejs.org/api/array

Get Selected Item in JavaScript Form

Somehow JavaScript mixed objects with attributes. For instance:

document.formName.listBoxName[i].selected

formName and listBoxName are references to two bojects. It might be good, but it just crosses the boundary of reference to object and the attributes. Don't know if this the the reason, to get selected item's value in form seems not easy. Google search shows there are so many people ask the question and not get right answers. Here is the easier way:

; function getValueOfSelectedItem(obj)
{ ; var val = obj.options[obj.selectedIndex].value
; if (val) (use val here)
}

To call this function, put the caller on onchange in HTML codes:

onChange="getValueOfSelectedItem(this)"

The beauty of it is there is no mixture of reference and attribute and you can pass anything of it without worry of crossing boundary issue.


http://www.java2s.com/Code/JavaScriptReference/Javascript-Properties/selectedIndexExample.htm

Turning SSRS Report Into Form

The difference between report and form is report pulls data out from database and the form is used to feed data into database. SQL Server Reporting Services is of the report. However, sometimes the two-way interactions are really needed. Here is an example. A parameter need to be input by user; however, if the user had input previously, it should be stored in database and no longer require user to input again.

The logic of the solution is:

1. Get value A of the subject from database according to other parameters.
2. If (Null!=A) then show report based on A, and exit.
3. Else if user input parameter B, then insert B into database, then show report based on B, and exit.
4. Else show the blank report with notice that user needs to key-in the B.

However, this logic does not allow front end to alter the what was already in database. Any change will be manully operated by back end. Alternatively, following logic can be applied:

1. If user input parameter B, then insert or alter B in database, then show report based on B, and exit.
2. Else get value A of the subject from database according to other parameters.
3. If (Null!=A) then show report based on A, and exit.
4. Else show the blank report with notice that user needs to key-in the B.

As a standard procedure, the user therefore is not required to key-in the parameter unless is notified.

INSERT and SET query can be as text or as stored procedure. However, INSERT query should not be stand along as text, or an error message will be generated. At the end, SSRS is of report.

Conservative Forecast Based On Historic Data

You can always use mean on the historic data as your forecast, which is reasonable. However, this is radical, especially when not consider the probability distribution. To be conservative, you may need to add a standard deviation (σ):

Mean + σ
Or
Mean - σ

In general, 1 standard deviation is good enough. In normally distributed data, 1σ means the side coverage of 34.1%, accounts for 84.1% of total population.

If there is no noise data within the dataset, arithmetic mean (average) can be used. However, if there is noise data, interquartile mean (IQM) is recommended. Accordingly, the standard deviation should be also based on the interquartile range (middle 50%).

In MySQL, the built-in function is STD(expr). In Oracle, it is STDDEV(expr) and in T-SQL, it is STDEVP(expr).

http://en.wikipedia.org/wiki/Standard_deviation
http://koncordpartners.blogspot.com/2010/11/practical-mean.html
http://oreilly.com/catalog/sqlnut/chapter/ch04.html
http://www.devguru.com/technologies/t-sql/7097.asp

Practical Mean

In statistics, mean has two related meanings:
- the arithmetic mean.
- the expected value of a random variable, which is also called the population mean.

To get the mean for a column in database, in general built-in aggregation function AVG() is good enough. However, one much understand this function is of arithmetic mean. If your database contains noise data, this is not good enough, simply because this mean does not have noise data prune mechanism. While different means would have their precise meaning, if you do not know which to use, use interquartile mean (IQM).

Following is the some notes related to T-SQL’s mean functions:

Arithmetic mean (AM)
There is built-in function – Never use DISTINCT, and no need to use ALL because it is default:

AVG ( [ ALL | DISTINCT ] expression )

Median
Median is not mean, but it is included here anyway. There is no such function in T-SQL. But you can get from here (credits to Itzik Ben-Gan):

SELECT(
(SELECT MAX(Value) FROM
(SELECT TOP 50 PERCENT Value FROM dbo.VOrders ORDER BY Value) AS H1)
+
(SELECT MIN(Value) FROM
(SELECT TOP 50 PERCENT Value FROM dbo.VOrders ORDER BY Value DESC) AS H2)
) / 2 AS Median;

Interquartile mean (IQM)
There is no such function in T-SQL. But you can get from here:

SELECT AVG(S1_2) AS P1_2
FROM Minut
WHERE S1_2 IS NOT NULL
AND Minut.Trip_Id NOT IN
(SELECT TOP 25 PERCENT Trip_Id FROM Minut WHERE S1_2 IS NOT NULL ORDER BY S1_2)
AND Minut.Trip_Id NOT IN
(SELECT TOP 25 PERCENT Trip_Id FROM Minut WHERE S1_2 IS NOT NULL ORDER BY S1_2 DESC)

If the dataset is so small, such as only a few records exist, SELECT TOP 25 PERCENT won't work. Instead, use following solution:

SELECT AVG(S1_2) AS P1_2
FROM Minut
WHERE S1_2 IS NOT NULL
AND Minut.Trip_Id NOT IN
(
SELECT TOP
(
SELECT CONVERT(INT, COUNT(*)/4)
FROM Minut
WHERE S1_2 IS NOT NULL
) Trip_Id
FROM Minut
WHERE S1_2 IS NOT NULL
ORDER BY S1_2
)
AND Minut.Trip_Id NOT IN
(
SELECT TOP
(
SELECT CONVERT(INT, COUNT(*)/4)
FROM Minut
WHERE S1_2 IS NOT NULL
) Trip_Id
FROM Minut
WHERE S1_2 IS NOT NULL
ORDER BY S1_2 DESC
)


http://en.wikipedia.org/wiki/Mean
http://blogical.se/blogs/mikael_sand/archive/2009/07/24/t-sql-is-mean-there-is-no-median.aspx
http://www.sqlmag.com/article/tsql3/calculating-the-median-gets-simpler-in-sql-server-2005.aspx
http://koncordpartners.blogspot.com/2010/12/rounding-issue-in-select-top-n-percent.html

Can JavaScript Codes Be Added To SSRS Report?

The SQL Server Reporting Services HTML is poorly constructed so that the tags you'd most want to customize don't have Id's or Classes assigned. In addition, the ASPX pages just reference compiled assemblies, so the only real way to modify them is via CSS. Someone tried to edit the ReportingServices.js file, but it is neither the concept of customization nor standard functionality.

Conclusion: you could not add JavaScript block onto SSRS.



http://geekswithblogs.net/mnf/archive/2007/11/25/sql-server-reporting-services-notes.aspx
http://geekswithblogs.net/mnf/archive/2007/11/25/sql-server-reporting-services-notes.aspx
http://stackoverflow.com/questions/789303/is-it-possible-to-embed-javascript-into-an-ssrs-report

Schedule A Database Job In MySQL

As of MySQL 5.1, one can use event to schedule a job:

CREATE EVENT event_name
ON SCHEDULE schedule
DO event_body
;

schedule can be: AT timestamp [+ INTERVAL interval] ...
or EVERY interval
[STARTS timestamp [+ INTERVAL interval] ...]
[ENDS timestamp [+ INTERVAL interval] ...]

interval can be: quantity followed by unit
unit can be: {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}

event_body can be SQL query or EXECUTE sp_name.

For instance:
CREATE EVENT event_name
ON SCHEDULE EVERY 5 MINUTE
DO SELECT * FROM tab
;

ALTER, DROP and SET GLOBAL event_name = 1 to switch on the event, etc.


http://dev.mysql.com/doc/refman/5.1/en/create-event.html
http://answers.oreilly.com/topic/177-how-to-use-events-to-schedule-database-actions-in-mysql/
http://rpbouman.blogspot.com/2005/10/scheduling-procedure-execution-in.html