MySQL Comments

Comments in SQL are used for explaining sections of statements or for disabling execution of SQL code.

Single Line Comments

Single line comments in MySQL start with –.

Any text following — until the end of the line will be ignored during execution.

Here’s an example using a single-line comment for explanation:

Example

— Select all:
SELECT * FROM Customers;

The following example uses a single-line comment to indicate that the rest of the line should be ignored:

Example

SELECT * FROM Customers — WHERE City=’Berlin’;

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

Example

— SELECT * FROM Customers;
SELECT * FROM Products;

Multi-line Comments

Multi-line comments in MySQL begin with /* and end with */.

Any text enclosed between / and */ will be ignored by the MySQL server.

Here’s an example using a multi-line comment for explanation:

Example

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

The following example uses a multi-line comment to disable multiple statements:

Example

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

To ignore a specific part of a statement, you can use the /* */ comment syntax.

Here’s an example that uses a comment to ignore part of a line:

Example

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

The following example uses a comment to exclude a portion of a statement:

Example

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;