Specifically for T-SQL, probably for other SQLs

SQL_cheatsheet.sql

-- Syntax order
-- https://learn.microsoft.com/en-us/sql/t-sql/queries/select-transact-sql

WITH cte AS (cte_query)
SELECT cols
FROM table 
WHERE cond
GROUP BY col
HAVING cond
WINDOW window_expr
ORDER BY col

-- Logical execution order
-- https://learn.microsoft.com/en-us/sql/t-sql/queries/select-transact-sql#logical-processing-order-of-the-select-statement

FROM
ON
JOIN
WHERE
GROUP BY
HAVING
SELECT
DISTINCT
ORDER BY
TOP


-- Check column unique 
-- Not considering duplicate NULLs
-- https://stackoverflow.com/questions/26199765/sql-query-to-determine-that-values-in-a-column-are-unique

SELECT COUNT(col), COUNT(distinct col) FROM table