SQL TOP, LIMIT, FETCH FIRST o ROWNUM Cláusula
La cláusula SQL SELECT TOP
La cláusula SELECT TOP se utiliza para especificar la cantidad de registros a devolver.
La cláusula SELECT TOP es útil en tablas grandes con miles de registros. Devolver una gran cantidad de registros puede afectar el rendimiento.
Ejemplo
Seleccione sólo los primeros 3 registros de la tabla Customers:
SELECT TOP 3 * FROM Customers;
Try it Yourself »
Note: Not all database systems support the SELECT TOP clause. MySQL supports the LIMIT clause to select a limited number of records, while Oracle uses FETCH FIRST n ROWS ONLY and ROWNUM.
SQL Server / MS Access Syntax:
SELECT TOP number|percent column_name(s)
FROM table_name
WHERE condition;
MySQL Syntax:
SELECT column_name(s)
FROM table_name
WHERE condition
LIMIT number;
Oracle 12 Syntax:
SELECT column_name(s)
FROM table_name
ORDER BY column_name(s)
FETCH FIRST number ROWS ONLY;
Older Oracle Syntax:
SELECT column_name(s)
FROM table_name
WHERE ROWNUM <= number;
Older Oracle Syntax (with ORDER BY):
SELECT *
FROM (SELECT column_name(s) FROM table_name
ORDER BY column_name(s))
WHERE ROWNUM <= number;
Demo Database
Below is a selection from the Customers table used in the examples:
| CustomerID | CustomerName | ContactName | Address | City | PostalCode | Country |
|---|---|---|---|---|---|---|
| 1 |
Alfreds Futterkiste | Maria Anders | Obere Str. 57 | Berlin | 12209 | Germany |
| 2 | Ana Trujillo Emparedados y helados | Ana Trujillo | Avda. de la Constitución 2222 | México D.F. | 05021 | Mexico |
| 3 | Antonio Moreno Taquería | Antonio Moreno | Mataderos 2312 | México D.F. | 05023 | Mexico |
| 4 |
Around the Horn | Thomas Hardy | 120 Hanover Sq. | London | WA1 1DP | UK |
| 5 | Berglunds snabbköp | Christina Berglund | Berguvsvägen 8 | Luleå | S-958 22 | Sweden |
LIMIT
The following SQL statement shows the equivalent example for MySQL:
Ejemplo
Select the first 3 records of the Customers table:
SELECT * FROM Customers
LIMIT 3;
Try it Yourself »
FETCH FIRST
The following SQL statement shows the equivalent example for Oracle:
Ejemplo
Select the first 3 records of the Customers table:
SELECT * FROM Customers
FETCH FIRST 3 ROWS ONLY;
SQL TOP PERCENT Ejemplo
The following SQL statement selects the first 50% of the records from the "Customers" table (for SQL Server/MS Access):
The following SQL statement shows the equivalent example for Oracle:
Ejemplo
SELECT * FROM Customers
FETCH FIRST 50 PERCENT ROWS ONLY;
ADD a WHERE CLAUSE
The following SQL statement selects the first three records from the "Customers" table, where the country is "Germany" (for SQL Server/MS Access):
The following SQL statement shows the equivalent example for MySQL:
The following SQL statement shows the equivalent example for Oracle:
Ejemplo
SELECT * FROM Customers
WHERE Country='Germany'
FETCH FIRST 3 ROWS ONLY;
ADD the ORDER BY Keyword
Add the ORDER BY keyword when you want to sort the result, and return the first 3 records of the sorted result.
For SQL Server and MS Access:
Ejemplo
Sort the result reverse alphabetically by CustomerName, and return the first 3 records:
SELECT TOP 3 * FROM Customers
ORDER BY CustomerName DESC;
Try it Yourself »
The following SQL statement shows the equivalent example for MySQL:
The following SQL statement shows the equivalent example for Oracle:
Ejemplo
SELECT * FROM Customers
ORDER BY CustomerName DESC
FETCH FIRST 3 ROWS ONLY;
