Merge and truncate in sql, PL-SQL Programming

Assignment Help:

MERGE and TRUNCATE in SQL

SQL has two more table update operators, MERGE and TRUNCATE. MERGE, like INSERT, takes a source table s and uses it to update a target table t. Briefly, a MERGE statement specifies a matching condition to determine which rows of s have at least one matching row in t (under that specified matching condition). It then specifies an open-ended series of conditions to be applied to each row of s paired with actions to be applied on t.

WHEN MATCHED AND c1 THEN x1 specifies that action x1, necessarily an UPDATE or DELETE, is to be applied on t for each matching row in s that satisfies the condition c1. WHEN NOT MATCHED AND c2 THEN x2 specifies that action x2, necessarily an INSERT, is to be applied on t for each non-matching row in s that satisfies the condition c2. The curiously named TRUNCATE statement deletes all the rows from its specified target, bypassing any triggered actions, including compensatory actions, specified for that target. The target must be a base table.


Related Discussions:- Merge and truncate in sql

Transaction context, Transaction context As the figure shows, the majo...

Transaction context As the figure shows, the major transaction shares its context with the nested transactions, but not with the autonomous transactions. Similarly, If one aut

Indeterminacy in sql, Indeterminacy in SQL Some SQL expressions are ac...

Indeterminacy in SQL Some SQL expressions are actually not function invocations at all in the mathematical sense, being indeterminate-invocations operating on identical input

Managing cursors, Managing Cursors The PL/SQL uses 2 types of cursors: ...

Managing Cursors The PL/SQL uses 2 types of cursors: implicit and explicit. The PL/SQL declares a cursor implicitly for all the SQL data manipulation statements, including th

Product-specific packages in pl/sql, Product-specific Packages The Ora...

Product-specific Packages The Oracle and different Oracle tools are supplied with the product-specific packages which help you to build the PL/SQL-based applications. For illu

Difference between implicit and explicit cursor, Implicit Cursor is declare...

Implicit Cursor is declared and used by the oracle environment internally. while the explicit cursor is declared and used by the external user. more over implicitly cursors are no

Negation - sql, Negation (NOT, ¬) - SQL There are three rows instead o...

Negation (NOT, ¬) - SQL There are three rows instead of just two. As you can see, ¬ p is defined as in two-valued logic (2VL) when p is either true or false, but ¬ (unknown) i

Initializing objects in pl sql, Initializing Objects: Till you initiali...

Initializing Objects: Till you initialize an object by calling the constructor for its object type, the object is automatically null. That is, the object itself is null, not me

What is a collection, What Is a Collection The collection is an ordered...

What Is a Collection The collection is an ordered group of elements, all of similar type (for e.g. the grades for a class of students). Each element has a unique subscript whic

Program, heap sort program in pl/sql

heap sort program in pl/sql

Defining ref cursor types, Defining REF CURSOR Types To make cursor va...

Defining REF CURSOR Types To make cursor variables, you take 2 steps. At first, you define a REF CURSOR type, and then declare the cursor variables of that type. You can defin

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd