For web development generally and for PostgreSQL syntax highlighting in particular I recommend Sublime text editor over its two biggest competitors, Atom text editor and VSCode. To install the native Sublime text editor snap package (currently version 3.1.1) in all currently supported versions of Ubuntu open the terminal and type:
sudo snap install sublime-text --classic
After Sublime text editor is installed it can be opened from the Dash by clicking on the Sublime icon or from the terminal with subl . The Sublime text editor snap package will be updated automatically when updates are available.
The PostgreSQL syntax highlighting in Sublime text editor is smarter and much easier to read than the SQL syntax highlighting in Atom text editor. Install the PostgreSQL Syntax Highlighting plugin in Sublime text editor as follows:
Select Tools -> Install Package Control to install Package Control.
Select Tools -> Command Palette.
In the Command Palette select the Package Control: Install Package option. This changes the Command Palette to show a list of installable packages. Find and click to install PostgreSQL Syntax Highlighting plugin which is marked by the mouse cursor in the below screenshot.

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Restart Sublime Text editor.
1337 Color Scheme looks more like what you want PostgreSQL syntax highlighting to look like than the default Monokai color scheme. In the Command Palette select the Package Control: Install Package option and install the 1337 Color Scheme package. Select the 1337 Color Scheme in Preferences -> Color Scheme instead of the default Monokai color scheme for PostgreSQL. This changes the color scheme for the file that you are working on without changing the default Monokai color scheme for all other files.
To select SQL syntax highlighting in Sublime text editor select View -> Syntax -> SQL (PostgreSQL).

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This is what it needs to look like.