Inner join, PL-SQL Programming

Assignment Help:

Inner Join

We have learned how to retrieve data from one table by using SELECT statement. But, as we have learned, normalized relational databases mean the data is spread between multiple related tables. Consequently, we need to learn how to select data from more than just one table. To get complete sets of data, we will need to use the SQL JOIN clause in SELECT statement. The normal form of SQL JOIN clause in MySQL is shown here:

 SELECT column_list FROM table_1

 [INNER | LEFT | RIGHT] table_2 ON conditions_2

 [INNER | LEFT | RIGHT] table_3 ON conditions_3 ...

 WHERE conditions

After SELECT keyword is a list of column names from which you want to retrieve the data. These columns have to be in the tables you select such as table_1, table_2... It is a best practice to explicitly declare the column using the table_name.column_name syntax. This will prevent a scenario where the same column name occurs in multiple tables, causing an ambiguous reference. Next you will list the main table and then a list of table you want to join. You can use INNER JOIN, LEFT JOIN or RIGHT JOIN. You can join a table with more than two tables or even with itself. In the JOIN clause you have to declare the join conditions. If all the conditions on each join clause match, MySQL will return the corresponding data.


Related Discussions:- Inner join

Avoiding collection exceptions, Avoiding Collection Exceptions   In ma...

Avoiding Collection Exceptions   In many cases, if you reference a nonexistent collection element, then PL/SQL raises a predefined exception. Consider the illustration shown b

%found - explicit cursor attributes, %FOUND Subsequent to a cursor or ...

%FOUND Subsequent to a cursor or cursor variable is opened but before the first fetch, the %FOUND yields NULL. Afterward, it yields TRUE when the last fetch returned a row, or

Semijoin and composition - sql, Semijoin and Composition - SQL For sem...

Semijoin and Composition - SQL For semijoin, the dyadic relational operator MATCHING, defined thus: r1 MATCHING r2, where r1 and r2 are relations such that r1 JOIN r2 is de

What is a record, What Is a Record  ? A record is a group of related...

What Is a Record  ? A record is a group of related data items that stored in the fields, each with its own name and datatype. Assume that you have different data about an em

Pl/sql expressions , Pl/SQL Expressions The Expressions are constructed...

Pl/SQL Expressions The Expressions are constructed by using the operands and operators. An operand is a constant, literal, variable, or function call which contributes a value

Dbms, DBMS: The answer to this question is of course given in of the t...

DBMS: The answer to this question is of course given in of the theory book. This book is concerned with SQL DBMSs and SQL databases in particular. Soon we will be looking a

Synonyms- naming conventions, Synonyms You can create the synonyms to pr...

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,

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

How exceptions propagate in pl/sql programming?, How Exceptions Propagate ?...

How Exceptions Propagate ? Whenever an exception is raised, and if the PL/SQL cannot find a handler for it in the present subprogram or block, the exception propagates. That is

Creating and destroying base tables, Creating and Destroying Base Tables: ...

Creating and Destroying Base Tables: Example shows an SQL command to create the base table counterpart of the ENROLMENT variable Example  Creating a base table. CREATE T

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