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!
WHEN or THEN Key Constraints
Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having been the case. A salary history table for employees, with columns From and To for dates defining the applicable time periods, would be a good example.
A constraint is needed to avoid the possibility of an employee being shown as having two different salaries on the same day, which could happen if two rows for the same employee have overlapping periods indicated by their From and To dates. The term "WHEN/THEN constraint" appeals to the notion of "unpacking" the table so that each row is replaced by one or more rows, one for each date contained in its from-to period: when the relation is unpacked, then the given key constraint (e.g., on employee number and date) is to hold.
Using the BULK COLLECT Clause The keywords BULK COLLECT specify the SQL engine to bulk-bind output collections before returning them to the PL/SQL engine. You can use these ke
Logical Connectives - SQL SQL's extended truth tables in which the symbol, for unknown, appears along with the usual T and F. Negation (NOT, ¬) Conjunction (
What Are Subprograms? The Subprograms are named PL/SQL blocks which can take parameters and be invoked. The PL/SQL has 2 types of subprograms known as the procedure s and func
Using FOR UPDATE If you declare a cursor which will be referenced in the CURRENT OF clause of an UPDATE or DELETE statement, you should use the FOR UPDATE clause to obtain an
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
Closing a Cursor The CLOSE statements disable the cursor, and the result set becomes undefined. An illustration of the CLOSE statement as shown: CLOSE c1;
Name Resolution In potentially uncertain SQL statements, the names of the database columns take precedence over the names of the local variables and formal parameters. For e.g.
THEO R Y OF CATASTROPHISM OR CATALYSM (CUVIER 1769-1832) - The world has passed thorugh several stages and at the end of each stage there was a catastrophe killing all the
Effects of NULL for Multiple Assignments - SQL If the row expression given as the source for a multiple assignment evaluates to NULL, then NULL is assigned to each target. If
Declaring and Initializing Objects: An object type is once defined and installed in the schema; you can use it to declare the objects in any PL/SQL, subprogram, block or packa
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: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd