![]() Strive to update our BC Oracle support information. All legitimate Oracle expertsĮrrata? Oracle technology is changing and we Independently investigate their credentials and experience, and not rely onĪdvertisements and self-proclaimed expertise. This book includes scripts and tools to hypercharge Oracle 11gĭocumentation was created as a support and Oracle training reference for use by ourĭBA performance tuning consulting professionals.Ĭonsidering using the services of an Oracle support expert should Oracle documentation notes the following syntax for decode:įilled with valuable information on Oracle SQL Tuning. By using decode to change the ranges to a binary number, we can then use the sum built-in function to count the number of values within a specified range. The power of these functions become apparent when combined with the decode built-in function. The case statement is an easier form of the decode statement. Oracle added the case function to SQL starting in Oracle9i to simplify this type of data transformation. Once we have converted the column to a 0-1 numeric value, we pass the entire clause to the sum function, and add-up the numbers.Īs we can see, the decode function is convoluted and hard to write. This is a very important SQL statement because it demonstrates the nesting of BIFs and the use of decode for counting values. Sum(decode(book_type,'miscellaneous',1,0)) miscellaneous, Sum(decode(book_type,'management',1,0)) management, Sum(decode(book_type,'fiction',1,0)) fiction, Sum(decode(book_type,'computer',1,0)) computer, Initcap(substr(pub_name,1,20)) publisher_name, Here is the SQL to create this report in your pubs database: The default value tells decode what to display if a column values is not in the paired list. ![]() At the end of the decode statement we find a default value. Note that Oracle decode starts by specifying the column name, followed by set of matched-pairs of transformation values. Here is how we do this with the decode function: When we run SQL queries, we want to transform these values into North, South, East and West. For example, say we have a column named REGION, with values of N, S, W and E. The Oracle decode statement was developed to allow us to transform data values at retrieval time. Let's take a look at how the decode statement works. Oracle started with the decode statement and later refined it in Oracle9i, morphing it into the case statement. One of the most amazing features of the case the Oracle decode statements is that they allow us to create an index on data column values that do not exist in the database. The Oracle decode and case functions are used within the Oracle database to transform data values for one value to another. Display the sales rep name and their hire date.The most powerful of all of the BIFs are the Oracle decode and Oracle case function. Instead, you must use single-line functions to solve the problem. You CANNOT use the keywords: BETWEEN, AND, OR. ![]() Find all the SalesReps who were hired during this period, so we can continue our investigation. Unfortunately, we are not sure if this date is accurate! (OH NO!) We definitely know it was within 2 months (plus or minus) from that date. Here is an example: CREATE TABLE SalesRepsĬONSTRAINT SalesrepsPK PRIMARY KEY (Salesrep) Select decode(1, '1', 'OK') from dual - OK For example: select case 1 when '1' then 'OK' end from dual - ERROR types of arguments can be different in DECODE (some rules still exist) while in CASE all exps & results should be from the same type group. you can compare NULL with DECODE: decode(col, NULL, 'undefined') CASE WHEN conditon1 THEN res1 ELSE res2 END (if condition1 then res1 else res2).CASE exp1 WHEN exp2 THEN res1 ELSE res2 END (if exp1 = exp2 then res1 else res2).= CASE WHEN promo_category = 'G1' THEN promo_cost *.25 ELSE NULL ENDĭECODE is similar to CASE, but usually more compact. = CASE WHEN promo_cost = 10000 THEN DECODE(promo_category, 'G1', promo_cost *.25, NULL) ELSE NULL END DECODE(promo_category, 'G1', promo_cost *.25, NULL) = CASE WHEN NVL(promo_cost,0) = promo_cost THEN promo_cost * 0.25 ELSE 100 END DECODE(promo_cost,10000, DECODE(promo_category, 'G1', promo_cost *.25, NULL), NULL) ![]() DECODE(NVL(promo_cost,0),promo_cost, promo_cost * 0.25, 100) "Discount" ![]()
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