Does the order of columns matter when creating a composite index?

Yes, the order of columns in a composite index matters. The index is built based on the sequence of the specified columns, and its effectiveness depends on how queries are executed.

For example, if you have an index on columns (A, B), it is efficiently used for queries filtering by A or by both A and B, but not for queries filtering only by B.

Therefore, when creating a composite index, it is important to consider which columns are most frequently used in WHERE conditions and in what order, so that the index maximally speeds up the necessary queries.