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Aprenda Combinando Resultados de Tabelas | Subconsultas Aninhadas
SQL Intermediário

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Combinando Resultados de Tabelas

Tarefa
test

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Your task will be to combine the employees and contractors tables using the UNION clause.

After that, from the resulting table, you should retrieve only those IDs that are multiples of 2. Also, you need to retrieve the first_name and last_name columns. Use the syntax WHERE id % 2 = 0. For this task, you need to use subqueries in the FROM section just as shown in the example.

Note

As a result, you should have 3 columns: id (an alias for the ID from both tables), first_name, last_name.

Brief Instructions

  • Retrieve the id, first_name, and last_name columns.
  • In the FROM clause, write two inner queries joined by the UNION clause.
  • In the first inner query, select employee_id, first_name, and last_name from the employees table.
    • Assign the alias id to employee_id.
  • In the second inner query, select contractor_id, first_name, and last_name from the contractors table.
    • Assign the alias id to contractor_id.
  • Assign the alias combined to both inner queries.
  • Finally, use a WHERE clause with the condition id % 2 = 0.

Solução

SELECT id, first_name, last_name
FROM (
(SELECT employee_id AS id, first_name, last_name
FROM employees)
UNION
(SELECT contractor_id AS id, first_name, last_name
FROM contractors)
) AS combined
WHERE id % 2 = 0
Tudo estava claro?

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Seção 2. Capítulo 6
SELECT ___, ___, ___
FROM (
-- write an inner subquery here
) AS combined
-- don't forget to write the WHERE clause here
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