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By Chris on August 9, 2014
When you are handling string you sometime have single quote in your string. I was looking on how to handle that in Oracle and it’s not pretty but you can cover that case with the chr(39) function, 39 being the code for the single quote.
So it you are looking the “it’s” you have to look for “it‘||CHR(39)||’s”
I’ve read I’ve could have use 2 quote or the $ in latter version. In that case:
SELECT 'it''s' name FROM DUAL;
Or use the new (10g+) quoting method
SELECT q'$it's$' NAME FROM DUAL;
Note I’ve used the chr(39) and worked fine for me I didn’t try the other one, so good luck with that.
Posted in db, prog | Tagged oracle, quote, single quote, sql |
By Chris on August 2, 2014
I had in the past had to work with oracle and had to convert it to mysql. Unfortunately (or fortunately) that project was cancel but here are the bit of information I’ve found that I didn’t know about and made me lost a lot of time.
Oracle vs mySQL datatype edition
From mySQL Forum:
NUMBER Any NUMERIC
DEC Any NUMERIC
DECIMAL Any NUMERIC
NUMERIC Any NUMERIC
DOUBLE PRECISION Any NUMERIC
FLOAT Any NUMERIC
REAL Any NUMERIC
SMALLINT Any SMALLINT
VARCHAR <256 VARCHAR
VARCHAR2 <256 VARCHAR
CHAR <256 CHAR
VARCHAR2 >255 TEXT
VARCHAR >255 TEXT
CHAR >255 TEXT
LONG <256 VARCHAR
LONGRAW <256 VARCHAR
RAW <256 VARCHAR
LONG >255 TEXT
LONGRAW >255 TEXT
RAW >255 TEXT
DATE – DATETIME (Since DATE in oracle can include time information!)
From what we needed we had to
decimal(50,0) = NUMBER
decimal(22,0) = INTEGER
DATE = datetime
Now that I look at it I think It would have been better to turn them both to number.
The best course of action is to find a DBA and use tool for the job like omega sync like it’s recommended in the following stackoverflow thread.
Posted in db, prog | Tagged db, migration, mysql, oracle |
By Chris on July 19, 2014
The to_date function we talked earlier make a come back.
The wrong way to do it is :
SELECT field 1, field2, date_and_time,
FROM table1
WHERE date_and_time = '12-04-27'
you end up comparing string in that case to work you need to do the following:
SELECT field 1, field2, date_and_time,
FROM table1
WHERE date_and_time = to_date('12-04-27','yy-mm-dd')
I saw some example where user needed to use the TRUNC function on the date_and_time, so if it doesn’t work with the previous answer try using the TRUNC function.
Posted in db, prog | Tagged date, oracle, search, to_date |
By Chris on July 12, 2014
I was having problem making one of my SQL query work in ORACLE until I realize that I got the check on the date wrong. It seem that Oracle didn’t interpreted my query has I expected when handling a date with a greater or lesser than operator (< or >).
So this won’t work :
date_and_time <= '01-DEC-02'
After some digging I’ve found out that there is
But this will :
to_date('01-DEC-2002','dd-mmm-yyyy');
The
TO_TIMESTAMP can be used to, check the reference for more information: TO_TIMESTAMP reference and TO_DATE Reference
Posted in db | Tagged date, datetime, oracle, to_date |
By Chris on July 9, 2014
Really quick post to a problem I’ve got un hibernate when converting to mySQL, I’ve found that the problem was because we were using a generator class “sequence” and in mySQL we needed to use “assigned” or “increment” instead.
Note you might not have that problem in your project but that was preventing me from creating my ids my mySQL db.
What are that generator class thing, well it how you generate your id. In oracle it usally use a sequence (hence the setting was sequence in hibernate) and mySQL didn’t support sequence at the time I was trying to convert it.
Sequence is safer if any other program/person is going to insert into the database table. Increment is less safer solution (but portable, to those db that don’t support Sequence) and good for testing and\or getting started. There are better ways than using Increment for use in production.
Note that you could use the generationType.AUTO and hibernate will produce the best strategy for you db.
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
Related:
How to have multiple database in a eclipse Java project (candidjava)
Changing database from Hibernate (stackoverflow)
Hibernate Generator class (javaTpoint)
Posted in db | Tagged hibernate, java, mysql, oracle |
By Chris on November 18, 2013
Posted in inspiration | Tagged inspiration, motivation |
By Chris on September 16, 2013
I’ve stumbled upon that problem recently and couldn’t remember how to do it. Has you except it’s trivial to do and like most of what can be done in programming there more than one way to do it.
1- Good old jdk String 🙂
Since Java 1.5 you have the new String format method do something similar.
String.format(“%10s”, “bob”).replace(‘ ‘, ‘*’);
String.format(“%-10s”, “bassen”).replace(‘ ‘, ‘*’);
output:
*******bob
bassen****
2- Apache StringUtils
Apache StringUtils has several methods to do this too: leftPad, rightPad, center and repeat.
if you use Apache StringUtils you get this :
StringUtils.leftPad(“bob”, 10, “*”)
StringUtils.rightPad(“bassen”, 10, “*”)
you get the same result
*******bob
bassen****
3- Google library Guava
If you still want to use another 3rd party library there Google utils library Guava that have something for you too:
Strings.padStart(“bob”, 10, ‘*’);//Equivalent of leftPad
Strings.padEnd(“bassen”, 10, ‘*’); //Equivalent of rightPad
More info on the java doc : http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/base/Strings.html#padStart(java.lang.String, int, char)
Has you can see typically, to use these methods, you specify the String that you’d like to pad and the total size of the finished String. This total size includes the starting length of the String. You can specify an alternative padding character or characters via a third argument to these methods.
Posted in tips | Tagged Apache, format, Guava, java, String, StringUtils |
By Chris on September 9, 2013
For some reason the pc at work didn’t had the run command in the start menu.
I write it here so I won’t forget it again and to help you too 🙂
- Click on start menu.
- Select “Control Panel”.
- Click on “Personalization”.
- Click on “Taskbar and start menu”.
- Click on “Customize”.
- Now select the “Run command” check box.
- Click ok and select “Apply” in the next window
- click Ok again 🙂
That’s how you can add back the run command in the windows 7 start menu !!!
Posted in prog, tips, tips | Tagged run, run command, start menu, windows 7 |
By Chris on September 5, 2013
They’re always a question that comeback either in interview or when you are playing old code.
Why the hell are they using Vector over arrayList ?
Vector is a class that exists since the beginning of java (aka Java 1.0) it’s implement List. It seems to pollute old code and still use programmer that don’t know that there is better alternative.
Common knowledge and our teacher use to tell us that the difference between Vector and arrayList is that Vector is synchronized and ArrayList is not, which is true… But what it fails to explain is that you should not use Vector for synchronized operation either. Why ?
Because it’s synchronizes on each individual operation. That’s almost never what you want to do.
Normally if you really need synchronization you want to synchronize a whole sequence of operations, not just the individual operation.
Because even if the add, remove or get operation is synchronized you still need to have a lock to avoid anyone changing the collection at the same time (preventing those pesky ConcurrentModificationException) and it also slower because it lock on each access when once would be enough.
Instead use a ArrayList and use Collections.synchronizedList on your array list when you truly need synchronization.
If you want something more efficient that the Collections.synchronizedList and you are using JDK 1.5 and higher. There is a good concurrent collections that have been introduced in java 1.5. The name of that collection is CopyOnWriteArrayList, it’s highly efficient for high volume , low latency system.
While the Collections.synchronizedMap and Collections.synchronizedList, provide a basic conditionally thread-safe implementation of Map and List.
Several factors make them unsuitable for use in highly concurrent applications — their single collection-wide lock is an impediment to scalability and it often becomes necessary to lock a collection for a considerable time during iteration to prevent ConcurrentModificationExceptions.
The CopyOnWriteArrayList implementation provide much higher concurrency while preserving thread safety, with some minor compromises in their promises to callers. CopyOnWriteArrayList are not necessarily useful everywhere you might use ArrayList, but are designed to optimize specific common situations. Many concurrent applications will benefit from their use.
Posted in prog, tips | Tagged arraylist, collections, java, java.util.List, List, synchronization, synchronizedList, vector |
By Chris on September 2, 2013
http://blog.foundersnetwork.com/2013/01/how-quora-sent-us-82-10-of-our-visitors/
Story of a startup and how quora helped them bring visitors to the site.
http://slant.co/topics/what-is-the-best-architecture-for-building-a-web-service/
soap vs rest…
basicly every new provider use rest now a day…
http://antjanus.com/blog/seo/running-a-blog-what-i-did-wrong-and-right-in-2012/
incredible journey from 0 to 20k visitor/month.
What really interesting is how he self-evaluate himself, that really important.
Many point are really good to take action on and will probably worth revisiting when my blog readership grow bigger.
https://www.futureadvisor.com/401k/comics/top-three-beginning-investing-books
I love the way they propose book through an infographic/comics, I’ll try that with my business/blog
http://www.nature.com/news/nearby-star-is-almost-as-old-as-the-universe-1.12196
What actually great with that discovery is that it’s almost as old as the universe and has some heavy element in them which mean it was a second generation star.
it’s not surprising for small stars to live a long time (they burn quite slowly).
what’s surprising is that we don’t see any older than about 14 billion years old.
Posted in link, prog, tips | Tagged blog, quora, rest, seo, soap, star, startup, webservice |
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