Skip to main content

Selecting from the DUAL Table

DUAL is a table automatically created by Oracle along with the data dictionary.
DUAL is in the schema of the user SYS, but is accessible by the name DUAL to all
users. It has one column, DUMMY, defined to be VARCHAR2(1), and contains one
row with a value ’X’. Selecting from the DUAL table is useful for computing a
constant expression with the SELECT statement. Because DUAL has only one row,
the constant is returned only once. Alternatively, you can select a constant,
pseudocolumn, or expression from any table, but the value will be returned as
many times as there are rows in the table

Comments

Post a Comment

Popular posts from this blog

Oracle Developer Technical Interview Questions

Here i am putting all the questions i had faced during my interviews ... Interview at “3i InfoTech”, Chennai:  1) What is flow of execution of WHEN-NEW-FORM-INSTANCE, WHEN-NEW-BLOCK-INSTANCE, and WHEN-NEW-ITEM-INSTANCE? 2) What is PRE-QUERY and POST-QUERY? When these triggers will fire? 3) If the object library with some blocks and triggers if a form inherited that object library if u doesn’t need some trigger to be inherited the can u delete that trigger from that form? 4) How u can call a report from a form? Which property u has set in runtime? 5) If u create a relation between two blocks in the form what are all triggers it will create? 6) What is a ref cursor? 7) To call a form which type of built-ins u has to use? 8) What is the main difference between expand and variable property for a text item in reports. 9) In a report layout there is accepted and rejected fields and it has a parameter when u run the report based on the parameter the output should sh...
Post a Comment
Read more

Difference Between CASE and DECODE?

– CASE is a expression – DECODE is a function - CASE expression is ANSI SQL Statement - DECODE is specific to Oracle Syntax - CASE syntax contains WHEN and THEN  - DECODE will not have this - CASE allow expressions or Scalar Sub query Expressions inside the CASE statement - DECODE won't allow expressions inside the DECODE function
1 comment
Read more