Are you asking specifically about SQL code completion? If so, that isn't available out-of-the-box, and I'm not familiar enough with it myself to be comfortable adding it. If you've used RSyntaxTextArea's AutoComplete library some already, and feel ambitious, you can try to create your own, in which case I'd invite you to look at the C and Shell language supports in RSTALanguageSupport
. They're both pretty straightforward examples of adding code completion support to RSTA (provided what completions you want to make available are mostly static).
Also, if you do choose to go this route, if you'd like to share your implementation, I'd be happy to add it into the RSTALanguageSupport repository so others can benefit from your hard work. The only thing is you'd have to be comfortable with licensing your code LGPL