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