Conteúdo do Curso
Introduction to SQL
1. Retrieving Data
2. Sorting Retrieved Data
Introduction to SQL
Limiting Results
We know that the SELECT
operator can retrieve all rows from a table of all or the specific columns. However, what if we only need to fetch a specific number of rows?
Note
This can be achieved using different syntax in various database management systems. In our case, since we are using PostgreSQL, we should utilize the
LIMIT
clause.
In the example below, we extract the first 7 rows (in our case, the capitals of the countries) from the column.
Here's a short example of the country
table:
id | name | continent | region | surfacearea | capital | population |
---|---|---|---|---|---|---|
1 | Japan | Asia | Eastern Asia | 377829 | Tokyo | 126714000 |
2 | Latvia | Europe | NULL | 64589 | Riga | 2424200 |
3 | Mexico | North America | Central America | 1958201 | Mexico City | 98881000 |
4 | Netherlands | Europe | Western Europe | 41526 | Amsterdam | 15864000 |
... | ... | ... | ... | ... | ... | ... |
15 | Malta | Europe | Southern Europe | 316 | Valletta | 380200 |
Tarefa
From the ' country ' table, let's retrieve 3 distinct (unique) continent
values.
Tudo estava claro?
Conteúdo do Curso
Introduction to SQL
1. Retrieving Data
2. Sorting Retrieved Data
Introduction to SQL
Limiting Results
We know that the SELECT
operator can retrieve all rows from a table of all or the specific columns. However, what if we only need to fetch a specific number of rows?
Note
This can be achieved using different syntax in various database management systems. In our case, since we are using PostgreSQL, we should utilize the
LIMIT
clause.
In the example below, we extract the first 7 rows (in our case, the capitals of the countries) from the column.
Here's a short example of the country
table:
id | name | continent | region | surfacearea | capital | population |
---|---|---|---|---|---|---|
1 | Japan | Asia | Eastern Asia | 377829 | Tokyo | 126714000 |
2 | Latvia | Europe | NULL | 64589 | Riga | 2424200 |
3 | Mexico | North America | Central America | 1958201 | Mexico City | 98881000 |
4 | Netherlands | Europe | Western Europe | 41526 | Amsterdam | 15864000 |
... | ... | ... | ... | ... | ... | ... |
15 | Malta | Europe | Southern Europe | 316 | Valletta | 380200 |
Tarefa
From the ' country ' table, let's retrieve 3 distinct (unique) continent
values.
Tudo estava claro?