SQL Comments

SQL Comments

Comments are used to explain sections of SQL statements, or to prevent execution of SQL statements.

Single Line Comments

Single line comments start with --.

Any text between – and the end of the line will be ignored (will not be executed).

The following example uses a single-line comment as an explanation:

--Select all:
SELECT * FROM Customers;

The following example uses a single-line comment to ignore the end of a line:

SELECT * FROM Customers -- WHERE City='Berlin'; 

The following example uses a single-line comment to ignore a statement:

--SELECT * FROM Customers;
SELECT * FROM Products;

Multi-line Comments

Multi-line comments start with /* and end with */.

Any text between /* and */ will be ignored.

The following example uses a multi-line comment as an explanation:

/*Select all the columns
of all the records
in the Customers table:*/
SELECT * FROM Customers;

The following example uses a multi-line comment to ignore many statements:

/*SELECT * FROM Customers;
SELECT * FROM Products;
SELECT * FROM Orders;
SELECT * FROM Categories;*/
SELECT * FROM Suppliers;

To ignore just a part of a statement, also use the /* */ comment.

The following example uses a comment to ignore part of a line:

SELECT CustomerName, /*City,*/ Country FROM Customers;

The following example uses a comment to ignore part of a statement:

SELECT * FROM Customers WHERE (CustomerName LIKE 'L%'
OR CustomerName LIKE 'R%' /*OR CustomerName LIKE 'S%'
OR CustomerName LIKE 'T%'*/ OR CustomerName LIKE 'W%')
AND Country='USA'
ORDER BY CustomerName;