Steps for Retrieving data from multiple tables in PL/SQL

Step 1: CREATE TABLE Statement

The PL/SQL CREATE TABLE statement allows you to create and define a table.

Syntax:

The syntax for the CREATE TABLE statement in Oracle/PLSQL is:

CREATE TABLE table_name
( 
  column1 constraints,
  column2 constraints,
  ...
  column_n constraints
);

Step 2: INSERT Statement

The Oracle/PLSQL INSERT statement is used to insert a single record or multiple records into a table in Oracle.

Syntax:

The syntax for the Oracle/PLSQL INSERT statement when inserting a single record using the VALUES keyword is:

INSERT INTO table_name
(column1, column2, ... column_n )
VALUES
(expression1, expression2, ... expression_n );

The syntax for the Oracle INSERT statement when inserting multiple records using a SELECT statement is:

INSERT INTO table_name
(column1, column2, ... column_n )
SELECT expression1, expression2, ... expression_n
FROM source_table
[WHERE conditions];

PS: expressions are nothing but values that we want to insert into the table.

Step 3: SQL Queries with Joins to Retrieve Data from Tables

Oracle JOINS are used to retrieve data from multiple tables. An Oracle JOIN is performed whenever two or more tables are joined in an SQL statement.

There are 4 different types of Oracle joins:

• INNER JOIN
• LEFT OUTER JOIN
• RIGHT OUTER JOIN
• FULL OUTER JOIN

PL/SQL is “Procedural Language extensions to the Structured Query Language”. SQL is a popular language for both querying and updating data in relational database management systems (RDBMS). PL/SQL adds many procedural constructs to SQL language to overcome some limitations of SQL. In addition, PL/SQL provides a more comprehensive programming language solution for building mission-critical applications on Oracle Databases.

Retrieving data from multiple tables in PL/SQL mainly involves using SQL Joins, which allows to combination of rows from one or more tables based on the related column between them. Before going with the query of retrieving data from multiple tables make sure you have sufficient or basic knowledge about SQL joins.