What is the best text editor for HTML/XHTML/CSS/PHP/SQL on Ubuntu?

Take a look at Geany

gedit is a good multi-purpose editor, but it’s not so great for web development.
I’ve used gPHPEdit, Geany and Bluefish in the past, and Bluefish is the one to which I keep coming back.
gPHPEdit is very nice for PHP, but has no special SQL features as far as I can tell.

Software Center has a program called “MySQL Query Browser” which includes a “syntax highlighting SQL editor”, so that might be useful to you.

Of course, ed is the standard editor.

If you want everything and the kitchensink, and have powerful enough hardware, try PHPEclipse. There’s a lot of features, meaning that it takes a while to figure out, but once you’ve done that, it’s awesome.

I must say I did like Bluefish though, really light-weight , yet it has a decent amount of features.