Question 1
There are two tables:
How to get count of unique values from table t1?
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SELECT COUNT(DISTINCT(value)) FROM t1; |
Question 2
You have the following two tables:
- book (name, volume, author_id)
- author (name, age)
How to select all books with multiple volumes and age of author greater than 50?
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SELECT * FROM book b INNER JOIN author a ON a.id = b.author_id WHERE b.volume > 1 and a.age > 50; |