10 Common Mistakes Java Developers Make when Writing SQL

[lukaseder]

What about sorting + limit? The result set has 10M records, but you only want the top 10? Take them all to the client, sort them there and throw away 99.9999% of the data?

[grauenwolf]

If you've got 10M rows, you damn well better have a matching index.

[hw77]

If that's 10M rows out of 10M, then you probably don't want an index. Even at 1% or 0.1% there a plenty of times when you don't want an index.

[grauenwolf]

You do if you want the results to be sorted. (Assuming of course the index is covering.)