In SQL, comments are used to annotate SQL code with explanatory notes or to temporarily disable certain parts of the code without affecting its functionality. There are two types of comments commonly used in SQL:
--) and extend to the end of the line.
-- This is a single-line comment
SELECT * FROM employees; -- This is also a comment at the end of a line
/* and end with */. They can span multiple lines.
/*
This is a multi-line comment.
It can span across several lines.
*/
SELECT * FROM departments;
Comments are ignored by the SQL engine during query execution. They are typically used to document SQL code, explain the purpose of specific queries or parts of queries, or temporarily exclude certain parts of the code for debugging or testing purposes.
It's good practice to add comments to your SQL code to improve readability and maintainability, especially in complex queries or when collaborating with other developers. However, excessive commenting can clutter the code, so it's essential to strike a balance between providing useful comments and keeping the code clean.