MySQL 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;