SQL Comments

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SQL Comments

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

Note: Comments are not supported in Microsoft Access databases!

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:

Example

--Select all:
SELECT * FROM Customers;

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

Example

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

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

Example

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

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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:

Example

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

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

Example

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

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

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

Example

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

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The following example uses a comment to ignore part 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;

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