Suggest a good IDE (if one exists)
Not only syntax highlighting is needed, but also highlighting of possible errors in the code.
The most important thing is auto-substitution: names, types, attributes, etc. I use phpDesigner, but unfortunately there is no auto-substitution in SQL.
Answer 1, authority 100%
I strongly recommend dbForge Studio for SQL Server
Writing SQL can be time consuming, but performance can be improved:
Auto code completion - to quickly create SQL expressions.
SQL formatting - to follow the accepted coding style.
SQL Code Templates - for quickly saving and reusing code snippets.
Quick help with information about database objects.
Code navigation - quick jump using F12 to the variable description, object editor, etc.
Answer 2, authority 44%
You can also take a look:
Answer 3, authority 44%
The best, like a lot from JB (IMHO):
https://www.jetbrains.com/datagrip/
Answer 4, authority 11%
I prefer to use Valentina Studio
(http://valentina-db.com/en/valentina-studio-overview). Works great on poppy, Windows and Linux. Especially on Linux.
A decent SQL editor. Not to mention a bunch of other features that the free version has.