http://kwatog.com tech notes and general nonsense Tue, 31 Jan 2012 06:27:55 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 http://kwatog.com/blog/oracle/oracle-power-function/ http://kwatog.com/blog/oracle/oracle-power-function/#comments Tue, 08 Nov 2011 03:30:14 +0000 admin http://kwatog.com/?p=681 There are some pl/sql functions that you rarely use and we always forget the syntax.And here’s another example — the power function. You know, that’s the n to the power of x (n^x). Again, I feel a bit ashamed for forgetting this one. Here’s the syntax.


power(m,n);


whereby
m is the base.
n is the exponent.

Example

power(36,5);

will return 1679616

Take note that this function returns NUMBER as the data type. That means the maximum value can only be 1.0 x 10^126. Later versions (10g onwards) can use binary_double as the base which makes the function output binary_double. I don’t know where you would need that large number, though. Also, if m is negative, then n must be an integer.

In case you are asking where I need it, there’s this code conversion whereby I needed to use the power function to get the value of a particular character. The exponent(n) is not fixed so I needed this function. To be specific, the function involves the pl/sql version of RowIdToRowIdNum of Siebel. I’ll post the code later.

References:

http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1594387900346571874

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]]> http://kwatog.com/blog/oracle/oracle-power-function/feed/ 0 http://kwatog.com/blog/oracle/select-random-records-in-oracle/ http://kwatog.com/blog/oracle/select-random-records-in-oracle/#comments Mon, 23 Feb 2009 06:32:09 +0000 admin http://kwatog.com/?p=47 Recently, I needed to sort the result of a query in random and show a limited number of records. Honestly, I didn’t know how to do it and had to search various online forums to get the correct answer. So for my own sanity, I’ll be posting the solution here.

Step 1
SELECT field_name1, field_name2
FROM table_name
WHERE field_query1 = 'ARGUMENT VAL'
ORDER BY dbms_random.VALUE;

The key here is the function dmbs_random.VALUE that generates, you guess it, random number. Its value is then used for ordering. The second step is to limit the output by using ROWNUM as below.

Step 2
SELECT field_name1, field_name2
FROM (SELECT field_name1, field_name2
FROM table_name
WHERE field_query1 = 'ARGUMENT VAL'
ORDER BY dbms_random.VALUE)
WHERE ROWNUM < 11;

If you’ll notice, I used a subquery here. Why didn’t I just include the rownum inside the subquery? It is because I wanted the subquery to finish the random ordering first before limiting the output to 10.

Real World Example

SELECT order_num, pr_postn_id
FROM (SELECT order_num, pr_postn_id
FROM siebel.s_order
WHERE order_num LIKE 'V-%'
ORDER BY dbms_random.VALUE)
WHERE ROWNUM < 11;


I'll also need this similar solution for MySQL and will be discussed in my next post.

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