fenway

What's "it"?

Confirm that each of the inner queries runs as fast as possible first.

Why?

I'd recommend that you review some of the archived posts, as well as the tutorials on the main site.

You didn't make the field big enough... it's a SMALLINT, right? Make it INT UNSIGNED.

Still one each.

That's correct -- EXPLAIN will tell you which one it picked, or if it decided to merge them.

Then post your solution for the benefit of others.

Unless you use TIMESTAMP columns, time zones in mysql have no effect whatsoever on DATE/DATETIME.

1-way encryption is called hashing.

Use a LEFT JOIN... IS NULL.

There are literally hundreds of tutorials on this site and others that cover this -- and countless forum topics, too.

Technically yes, but why?

Did you change the delimiter?

Then type a where clause -- I don't see the issue.

How much time in seconds? You can compare timestamps.

And next time, don't post code unless you're asked to.

One quick look at the manual for CREATE TABLE will tell you exactly what's going on here.

MySQL will pick the "best" one to use, and it's not always the most desirable. MySQL 5 has index_merge, which will sometime generate a pseudo-index that can use multiple, but again, not always reliable.

Too hypothetical -- post EXPLAIN output.

Just use the "new" order, and you're done -- ignore the existing order.

You likely need to handle this in application code.

Look at mysqldump.

Define "not working" -- and you shouldn't be sending passwords in plaintext.

That's not even close to being true in the general case.