Inner join, PL-SQL Programming

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.

Posted Date: 2/16/2013 8:13:40 AM | Location : United States







Related Discussions:- Inner join, Assignment Help, Ask Question on Inner join, Get Answer, Expert's Help, Inner join Discussions

Write discussion on Inner join
Your posts are moderated
Related Questions
Updating Tables in SQL The topic of updating by describing the assignment operator, ":=" in Tutorial D. SQL uses a different syntax for assignment, using the key word SET and

Use Object Types and Collections The Collection types and object types increase your efficiency by allowing for the realistic data modeling. The Complex real-world entities an

Using a Host Variable You can declare the cursor variable in the PL/SQL host environment like an OCI or Pro C program. To use the cursor variable, you should pass it as a host

Attributes: Just similar to variable, an attribute is declared with a name and datatype. The name should be exclusive within the object type. The datatype can be any Oracle ty

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

Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri

1. Create a procedure called TAX_COST_SP to accomplish the tax calculation task. Keep in mind that the state and subtotal values are inputs into the procedure and the procedure is

Anatomy of a Table: Figure shows the terminology used in SQL to refer to parts of the structure of a table. As you can see, SQL has no official terms for its counterpa

Using LIMIT For nested tables, that have no maximum size, the LIMIT returns NULL. For varrays, the LIMIT returns the maximum number of elements that a varray can have (that yo

Table Represents an Extension - SQL It describes how each tuple in a relation represents a true instantiation of some predicate and each true instantiation is represented by s