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

Enrolment was split - sql, Enrolment was split - SQL Example shows ho...

Enrolment was split - SQL Example shows how relvars IS_CALLED and IS_ENROLLED_ON can be derived from the original ENROLMENT relvar, using projection in the initial assignment

Database Management, Due to an increase in overhead costs, the buying price...

Due to an increase in overhead costs, the buying price of all items needs to be increased. Management wants to see a report before deciding how much each product will go up. Add to

Database values-assignments in pl/sql, Database Values You can use the S...

Database Values You can use the SELECT statement to have the Oracle assign values to a variable. For Each and every item in the select list, there must be a matching, type-compa

Use external routines - improve performance of application, Use External Ro...

Use External Routines The PL/SQL is particular for the SQL transaction processing. Therefore, several tasks are more quickly completed in a lower-level language like C that is

Boolean values-assignments in pl/sql, Boolean Values Only the values TRU...

Boolean Values Only the values TRUE, FALSE, & NULL can be assigned to a Boolean variable. For illustration, given the declaration DECLARE done BOOLEAN; the following statements

Operators on tables and rows, Operators on Tables and Rows Row Extrac...

Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.

Use bulk binds - improve performance of application, Use Bulk Binds If...

Use Bulk Binds If SQL statements execute inside a loop using the collection elements as bind variables, context switching between the PL/SQL & SQL engines can slow down the ex

Maintain an audit trail of product table changes, The accuracy of product t...

The accuracy of product table data is critical and the Brwebean's. owner wants to have an audit file that contains information regarding all DML activity on the BB_PRODUCT table. T

Execute your documentation in oracle, Using research notes and Oracle docum...

Using research notes and Oracle documentation plan and execute an upgrade of an installation of Oracle 10g to Oracle 11g release 1. To do this you must show in screen shots and wri

Calculate the number of tuples, Question: (a) The objective of query opti...

Question: (a) The objective of query optimization is to choose the most efficient strategy for implementing a given relational query, thereby improving the system performance. On

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