Programming and Web Design

Join clause is used to combine rows from two or more tables depending upon common field between them. There are different kinds of Joins. The most common and useful Join is Inner Join. Inner Join: It will return all rows from multiple tables where the condition is met.

Aggregate Functions are those functions which are used in SQL. They return a single value which is calculated from values in the columns from a particular table. The aggregate functions are below: AVG()- It returns a average value COUNT() - It returns the number of rows in a table MAX() - It returns the maximum value stored in a table MIN() - It returns the minimum value stored in a table SUM() - It returns the sum of all the values of specified column

What are Cursors? A cursor is a temporary work area created in the system memory when a SQL statement is executed. A cursor contains information on a select statement and the rows of data accessed by it. This temporary work area is used to store the data retrieved from the database, and manipulate this data. A cursor can hold more than one row, but can process only one row at a time. The set of rows the cursor holds is called the active set. There are two types of cursors in PL/SQL: Implicit cursors: These are created by default when DML statements like, INSERT, UPDATE, and DELETE statements are executed. They are also created when a SELECT statement that returns just one row is executed.

Between Operator It is used to select values within a range.

A subquery is a query inside another query or it is a nested query which is embedded within the WHERE clause. Subqueries can be used with the SELECT, INSERT, UPDATE, and DELETE statements along with the operators like =, <, >, >=, <=, IN, BETWEEN etc.

Primary Key: Primary Key is something which will uniquely identifies each record in a database table.