What follows is an opinionated SQL style guide. This style has evolved during my career and will probably continue to evolve.
/* *************************************************************************************************
Description:
Author: Your name
Create Date: Date created
************************************************************************************************* */
select *--Annotate your code with comments!where statements as where 1=1 to aid quick commenting / uncommenting of filter conditions without having to juggle and statements-- inline comments should have a space between the second dash and the start of the comment
select
a.col1 -- indent first select column by three spaces
,a.col2 -- indent second select column by two spaces, and include comma at start of line
,a.col3
,b.col4
,sum(b.col5) as col5
from table1 a
/*
blank line between from and each join statement and comments
preceding join indicating why join is required.
*/
left join table2 b -- ANSI joins. Omit "outer" keyword for left and right joins.
on a.col1 = b.col1 -- indent join condition by 2 spaces
and a.col2 = b.col2
where 1=1 -- always use "where 1=1" to facilitate easier commenting/uncommenting of filters
and a.col3 = 'Condition 1'
and b.col4 != 'Condition 2' -- use != rather than <>
group by
a.col1
,a.col2
,a.col3
,b.col4
having sum(b.col5) > 100