Write Queries to Combine Tables Using Various Join Operations (inner, Left, Right, and So on) with Single or Multiple Keys, as Well as Set Operations Like Union and Union All, Including the Differences Between the Joins (inner, Left, Right, and So On). DATA-ANALYST-ASSOCIATE Practice Questions (Page 4)

Questions 16–20

1. 16foundation · easy

   If `SELECT 1 AS x UNION ALL SELECT 1 AS x` is executed, how many rows are returned?

   • A2
   • B0
   • C1
   • DAn error
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2. 17foundation · easy

   If `SELECT 1 AS x UNION SELECT 1 AS x` is executed, how many rows are returned?

   • A2
   • B1
   • C0
   • DAn error
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4. 18foundation · easy

   Which join type returns rows from the left table that have no match in the right table?

   • AINNER JOIN
   • BANTI JOIN
   • CSEMI JOIN
   • DLEFT JOIN
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5. 19foundation · easy

   Which of the following is an example of implicit comma syntax for an inner join?

   • ASELECT * FROM a LEFT JOIN b ON a.id = b.id
   • BSELECT * FROM a CROSS JOIN b
   • CSELECT * FROM a INNER JOIN b ON a.id = b.id
   • DSELECT * FROM a, b WHERE a.id = b.id
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6. 20foundation · easy

   In a query joining `customers` and `orders` with `INNER JOIN`, what happens to customers who have no orders?

   • AThey appear with NULL order columns.
   • BThey appear once with a placeholder row.
   • CThey are excluded from the result set.
   • DThey appear only if the orders table is empty.
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