[Solved] get statistics information by SQL query efficiently for table with 3 columns and 800 million rows
The OP probably already knows this, but here is how to get the answer, disregarding efficiency. First, cards per location, as described in the comments: SELECT locationid, COUNT(DISTINCT cardID) FROM table GROUP BY locationid Next the same thing per state. SELECT substring(locationid, 1, 2) state, COUNT(DISTINCT cardID) FROM table GROUP BY substring(locationid, 1, 2) For … Read more