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 Are Constraints Checked
Under the model constraints are conceptually checked at all statement boundaries (and only at statement boundaries). By default the same is true of SQL. However, SQL does not support the "multiple assignment" concept, described in the theory book, for database updates. For that reason it has to include an alternative method of addressing the problems that multiple assignment addresses. SQL does so by allowing the checking of specified constraints to be temporarily deferred and reinstated later-but never across a transaction boundary. As a result, it is possible for the database to appear to be inconsistent, but only to the user whose as yet uncommitted transaction has given rise to that state of affairs. As a consequence of deferred constraint checking, SQL code that depends on consistency with declared constraints is obviously exposed to that assumption of consistency being false when the code is executed while checking is deferred.
For example, the table expression SELECT Name FROM IS_CALLED WHERE StudentId = 'S1' might be expected never to result in a table containing more than one row, thanks to the key constraint applying to IS_CALLED; thus it might be used in a scalar subquery. However, if the checking of that key constraint is temporarily deferred and two or more rows with StudentId equal to 'S1' temporarily appear in that table, then the scalar subquery will give rise to a run-time exception. Fortunately, SQL does allow a constraint to be declared as NOT DEFERRABLE, and that is the default option.
Using INNER JOIN INNER JOIN is used to retrieve the data from all tables listed based on a condition of equality listed after keyword ON. If the condition is not meet, rows ar
Project Description: I want a small relational database to be built. I want the database to have the subsequent information tables: Employee Information Document storage
Project Description: I want to rebuild it and add better content to it It will include up to 5 forms The data will be saved on SQL server and the data access layer could b
Create a procedure named STATUS_SHIP_SP that allows a company to employee in the Shipping Department to update the status of an order to add shipping information. The BB_BASKETSTAT
Closing a Cursor Variable The CLOSE statement disables the cursor variable. After that, the related result set is undefined. The syntax for the same is as shown below: CLOS
Using DELETE This process has three forms. The DELETE removes all elements from the collection. DELETE(n) removes the nth element from the nested table. When n is null, then D
Keys in SQL SQL support for keys in the following respects: SQL does not require at least one key for every base table. If no key is explicitly declared, then KEY {ALL B
Manipulating Local Collections Within PL/SQL, to manipulate the local collection, by using the TABLE and CAST operators . The operands of CAST are a collection declared locally
Renaming Columns - SQL SQL has no direct counterpart of RENAME. To derive the table on the right in Figure 4.4 from the table on the left, Tutorial D has IS_CALLED RENAME ( St
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: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd