How to query data in oracle database

How to use SQL to query data in Oracle database: Use the "sqlplus" command to connect to the database; execute the "SELECT" statement and specify the columns and tables to be extracted; optional: use "ORDER BY", "LIMIT" " and functions to sort, limit, and manipulate results.

How to query data using Oracle Database

Querying is the process of obtaining specific data in the database. In Oracle Database, you query data by writing SQL (Structured Query Language) statements.

Steps:

1. Open a command prompt or terminal window.

2. Enter the following command to connect to the database:

<code>sqlplus username/password@host:port/database</code>

(replace "username", "password", "host", "port" and " database" as your actual value)

3. Enter the following query statement:

<code>SELECT column_list
FROM table_name
WHERE condition;</code>

(replace "column_list", "table_name" and "condition" with the required value)

Example:

To get the names of all customers in the "customers" table, you can use the following query:

<code>SELECT name
FROM customers;</code>

Query results:

The query results will be displayed in the command prompt or terminal window, usually in table format.

Other query options:

• Sort: Use the "ORDER BY" clause to sort the results, for example:

  <code>SELECT name
  FROM customers
  ORDER BY name DESC;</code>

  (Arrange names in descending order)

• Limit results: Use the "LIMIT" clause to limit the number of results returned, for example:

  <code>SELECT name
  FROM customers
  LIMIT 10;</code>

  (Return up to 10 records)

• Use functions: You can use functions to operate on data in queries, for example:

  <code>SELECT UPPER(name) AS uppercase_name
  FROM customers;</code>

  (Convert name to uppercase)

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