Select in Oracle | Full Structure, Tips and Tricks | SQL PLSQl

Pubblicato il: 16 febbraio 2024
sul canale di: Cloud Research & Software Engineering

The `SELECT` statement in Oracle SQL is used to retrieve data from one or more tables in a database. It is a fundamental component for querying and manipulating data. The `SELECT` statement consists of several key elements:

1. *SELECT Clause:*
Specifies the columns you want to retrieve from the table.
Syntax: `SELECT column1, column2, ... FROM table_name;`

2. *FROM Clause:*
Specifies the table or tables from which to retrieve data.
Syntax: `SELECT column1, column2, ... FROM table_name;`

3. *WHERE Clause:*
Optional, filters the rows returned based on a specified condition.
Syntax: `SELECT column1, column2, ... FROM table_name WHERE condition;`

4. *GROUP BY Clause:*
Groups rows that have the same values in specified columns.
Used with aggregate functions like COUNT, SUM, AVG, etc.
Syntax: `SELECT column1, column2, ... FROM table_name GROUP BY column1, column2, ...;`

5. *HAVING Clause:*
Similar to the WHERE clause but used with aggregate functions and applies conditions to grouped rows.
Syntax: `SELECT column1, column2, ... FROM table_name GROUP BY column1, column2 HAVING condition;`

6. *ORDER BY Clause:*
Sorts the result set based on specified columns and order (ASC for ascending, DESC for descending).
Syntax: `SELECT column1, column2, ... FROM table_name ORDER BY column1 [ASC|DESC], column2 [ASC|DESC], ...;`

7. *DISTINCT Keyword:*
Removes duplicate rows from the result set.
Syntax: `SELECT DISTINCT column1, column2, ... FROM table_name;`

8. *Joins:*
Allows you to retrieve data from multiple tables based on a related column.
Common types include INNER JOIN, LEFT JOIN (or LEFT OUTER JOIN), RIGHT JOIN (or RIGHT OUTER JOIN), and FULL JOIN (or FULL OUTER JOIN).

9. *Aliases:*
Provides a temporary name for a table or column to make the SQL statement more readable.
Syntax: `SELECT column1 AS alias_name FROM table_name;`

10. *Aggregate Functions:*
Functions like COUNT, SUM, AVG, MIN, MAX that perform calculations on a set of values.
Used with GROUP BY clause to summarize data.

These elements combine to form a powerful tool for querying and manipulating data in Oracle SQL.

In questa pagina del sito puoi guardare il video online Select in Oracle | Full Structure, Tips and Tricks | SQL PLSQl della durata di ore minuti seconda in buona qualità , che l'utente ha caricato Cloud Research & Software Engineering 16 febbraio 2024, condividi il link con amici e conoscenti, su youtube questo video è già stato visto 42 volte e gli è piaciuto 2 spettatori. Buona visione!

20,407

682