Queries - (Oracle Query)

In Oracle, queries are used to retrieve data from one or more database tables. Queries are written in SQL (Structured Query Language) and can be used to filter, sort, and manipulate data.

Syntax

The basic syntax for a query in Oracle is:

SELECT column1, column2, ...
FROM table_name
WHERE condition1 AND/OR condition2 ...
GROUP BY column1, column2, ...
HAVING condition1 AND/OR condition2 ...
ORDER BY column1, column2, ... ASC/DESC

Here, SELECT is used to specify the columns of data to retrieve, FROM is used to specify the table(s) to retrieve data from, WHERE is used to filter the data by one or more conditions, GROUP BY is used to group the data by one or more columns, HAVING is used to filter the grouped data by one or more conditions, and ORDER BY is used to sort the data by one or more columns in ascending or descending order.

Example

Here is an example of an Oracle query that retrieves all rows from a employees table:

SELECT *
FROM employees;

Output

The output of the above query would be all the rows of data from the employees table.

Explanation

In the above example, we have used the SELECT statement to retrieve all columns of data from the employees table. The * symbol is used as a wildcard to retrieve all columns. The FROM statement specifies the table to retrieve data from.

Use

Queries in Oracle are used to retrieve data from one or more database tables and are used to filter, sort, and manipulate data. Queries can be used to generate reports, perform analysis, and extract specific information from large databases.

Important Points

• Oracle queries are written in SQL.
• Queries are used to retrieve data from one or more database tables.
• Use SELECT to specify the columns of data to retrieve.
• Use FROM to specify the table(s) to retrieve data from.
• Use WHERE to filter the data by one or more conditions.
• Use GROUP BY to group the data by one or more columns.
• Use HAVING to filter the grouped data by one or more conditions.
• Use ORDER BY to sort the data by one or more columns in ascending or descending order.

Summary

In summary, Oracle queries are used to retrieve data from one or more database tables. Queries are written in SQL and can be used to filter, sort, and manipulate data. Understanding the syntax and use of queries are essential for working with large databases and generating reports and analysis.