The PL/SQL compiler ignores comments. You can use comments to document your source code.
You can disable obsolete or unfinished pieces of code by turning them into comments.
A single-line comment begins with -- and extends to the end of the line.
The following code has three single-line comments.
SQL> SQL> DECLARE-- from ww w . j a va 2s .c o m 2 howmany NUMBER; 3 num_tables NUMBER; 4 BEGIN 5 -- Begin processing 6 SELECT COUNT(*) INTO howmany 7 FROM USER_OBJECTS 8 WHERE OBJECT_TYPE = 'TABLE'; -- Check number of tables 9 10 DBMS_OUTPUT.PUT_LINE('howmany:' || TO_CHAR(howmany)); 11 12 num_tables := howmany; -- Compute another value 13 14 DBMS_OUTPUT.PUT_LINE('num_tables:' || TO_CHAR(num_tables)); 15 16 END; 17 / howmany:963 num_tables:963 PL/SQL procedure successfully completed. SQL>
In the following code, while testing or debugging a program, you can disable a line of code by making it a comment. For example:
-- DELETE FROM emp WHERE comm_pct IS NULL