How Can I Use the IN Clause to Query Multiple Columns in SQL?

Querying Multiple Columns in the IN Clause in SQL

When querying a database table based on a set of values for a given column, the IN clause is a convenient option. However, when dealing with multiple columns, the IN clause becomes unusable.

To overcome this challenge, the usual approach involves using joins or the EXISTS clause. However, these methods require both the main table and the search data to be present in the database.

Consider a use case where you have a User table with columns (firstName, lastName, City), and you need to retrieve the cities for a list of (firstname, lastName) tuples. Two potential solutions emerge:

Solution 1:

Construct a lengthy SELECT query involving OR conditions:

SELECT city FROM user WHERE (firstName=x and lastName=y) or (firstName=a and lastName=b) or ...

Solution 2:

Create a staging table containing all the firstName and lastName values and perform a join between the User table and the staging table.

Alternative Solution:

Fortunately, there's a straightforward way to query multiple columns using the IN clause:

SELECT city FROM user WHERE (firstName, lastName) IN (('a', 'b'), ('c', 'd'));

Sqlfiddle Demonstration:

[Sqlfiddle Demo]()

This solution effectively addresses the problem of querying multiple columns in the IN clause without resorting to joins or the EXISTS clause. It provides an efficient and concise approach to retrieving the desired data.

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