Order in Multi-Column Index Matters - Deepstash
Order in Multi-Column Index Matters

Order in Multi-Column Index Matters

Order of the columns matter.

The index is useless if the first column doesn't appear in the WHERE clause.

Example 1:

An index on (t, x) will not be used in this query:

  • SELECT * FROM table WHERE x = 11

Example 2:

However an index on (x, t) will be used in both of these queries:

SELECT * FROM table WHERE x = 11

and

SELECT * FROM table WHERE t = 9 and x = 11

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