Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Effects of NULL Operator
As a general rule-but not a universal one-if NULL is an argument to an invocation of a system-defined read-only operator, then NULL is the result of that invocation. As you can see, the code for HIGHER_OF includes A > B, an invocation of the system-defined read-only operator ">", which does follow the general rule. Hence, if NULL is substituted for either or both of the parameters A and B, then NULL- which in this case we can also call UNKNOWN because ">" is a Boolean operator-is the result of the invocation. You are perhaps now wondering how SQL handles the IF statement when the specified condition yields UNKNOWN: is the THEN clause evaluated, or is it the ELSE clause?
As you know, other programming languages are normally based on classical logic. In keeping with the existence of just two truth values, TRUE and FALSE, the syntax for IF statements (and IF expressions) in such languages has just the two forks, THEN for when the condition is TRUE, ELSE for when it is not (i.e., is FALSE). You might therefore reasonably expect a language that embraces n truth values to support a variety of IF that has n forks-under a language design principle that Fred Brooks referred to as conceptual integrity, which means adhering rigorously to the language's adopted concepts. Instead, SQL retains just the two forks, keeping the normal treatment of THEN as being the one for when the condition is TRUE and arbitrarily lumping UNKNOWN in with FALSE for the ELSE fork. You should now be able to see that the general rule ("NULL in, NULL out") for system-defined operators cannot be said to apply to user-defined ones. If A > B evaluates to UNKNOWN, then the result of the HIGHER_OF invocation is the argument substituted for B, which might or might not be NULL.
GOTO Statement The GOTO statement branches to a label unconditionally. The label must be exclusive within its scope and should precede an executable statement or a PL/SQL block.
Use the MASCOT tables CREDITRS, PORDS and PAYMENTS to write SQL queries to solve the following business problems. These tables / data are available to you via the USQ Oracle server
Using FIRST and LAST FIRST and LAST return the first and last (minimum and maximum) index numbers in a collection. When the collection is empty, the FIRST and LAST return NULL
Attributes: Just similar to variable, an attribute is declared with a name and datatype. The name should be exclusive within the object type. The datatype can be any Oracle ty
Perform the following queries on the Hospital1.DB using SQL Anywhere (START EARLY!). a. Which patients have purchased the drug "Tylenol"? List the names and addresses. Arrange the
How Exceptions Are Raised By the run-time system, the internal exceptions are raised implicitly as are user-defined exceptions that you have related with an Oracle error number
Scoping Within the similar scope, all the declared identifiers should be unique. So, even if their datatypes differ, the variables and parameters cannot share the similar name.
Synonyms You can create the synonyms to provide location transparency for the remote schema objects like tables, views, sequences, stand-alone subprograms, and packages. Though,
Example of EXCEPT Operator - SQL Example, like its counterpart in the theory book, illustrates the convenience of allowing any table expression to be the source for an INSERT
IN Operator The operator IN tests the set membership. This means "equal to any member of." The set may have nulls, but they are ignored. For illustration, the statement below do
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd