How Can I Efficiently Query Multiple Columns Using MySQL's IN Clause?

Querying Multiple Columns in an IN Clause with MySQL

When working with structured data, querying multiple columns within an IN clause is a common operation. However, for MySQL, there is a subtle distinction between using the IN clause with a single tuple and with a set of tuples.

Single Tuple Query:

The original question describes a scenario where you have four columns (x0, y0, x1, y1) representing geographical coordinates. For a single combination of values, such as (4, 3, 5, 6), you can use the IN clause as follows:

SELECT * FROM my_table WHERE (x0, y0, x1, y1) IN ((4, 3, 5, 6))

With a composite index on (x0, y0, x1, y1), this query will efficiently locate the desired row.

Multiple Tuple Query:

However, the question also involves querying a list of tuples, such as [(4, 3, 5, 6), (9, 3, 2, 1)]. For such scenarios, MySQL's optimizer may not always handle the IN clause optimally.

Optimizer Improvement in Newer MySQL Versions:

In earlier MySQL versions (prior to 5.7), the optimizer would break down the multiple tuple query into a series of OR clauses, as described in the provided answer:

(  ( x0 = 4 AND y0 = 3 AND x1 = 5 AND y1 = 6 ) 
OR ( x0 = 9 AND y0 = 3 AND x1 = 2 AND y1 = 1 )
)

This approach could lead to inefficient execution plans, especially with large datasets.

In newer versions of MySQL (5.7 and above), the optimizer has been improved to generate more efficient plans for multiple tuple IN queries. For these versions, using the following syntax is recommended:

(x0, y0, x1, y1) IN ((4, 3, 5, 6), (9, 3, 2, 1))

The optimizer will automatically generate an optimized execution plan that leverages the available index.

Conclusion:

When querying multiple columns in an IN clause with MySQL, the recommended approach depends on the MySQL version. For older versions, it is advisable to break down the query into OR clauses. For newer versions, the improved optimizer can handle multiple tuple IN queries efficiently without the need for manual restructuring.

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