Comments in MySQL

You can include comments in MySQL in three ways:

1. You can begin them with two hyphens followed by a blank space. These comments continue until the next line so a semi-colon at the end is ignored.
2. You can begin them with a hash (#). These comments continue until the next line so a semi-colon at the end is ignored.
3. You can begin them with a /* as in C. Comments like this continue until a */ and can span more than one line.

You can see what I mean in the examples below:

 

mysql> select 1-- valid comment;

    -> ;

+---+

| 1 |

+---+

| 1 |

+---+

1 row in set (0.00 sec)

 

mysql> select 2--invalid comment;

ERROR 1054 (42S22): Unknown column 'invalid' in 'field list'

mysql> select 3#another valid comment;

    -> ;

+---+

| 3 |

+---+

| 3 |

+---+

1 row in set (0.00 sec)

 

mysql> select 4/*in-line comment*/;

+---+

| 4 |

+---+

| 4 |

+---+

1 row in set (0.00 sec)

 

mysql> select 5/*multi-

   /*> line comment*/;

+---+

| 5 |

+---+

| 5 |

+---+

1 row in set (0.00 sec)

 

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