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Tools to manage and monitor MySQL databases

Meaning Of Dump Comments

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- June 14, 2007 at 10:48 am #10390
  
  maxhugen
  Participant
  
  I tried out a dump of the table structure, and noticed comment lines with what appears to be some sort of code in them, eg:
  
  /*!40101 SET NAMES utf8 */;
  
  Are these SQLyog-specific 'instructions' or what?
  
  MTIA
- June 14, 2007 at 11:20 am #24260
  
  peterlaursen
  Participant
  
  No, it is not SQLyog-specific. It is a MySQL extension to standard SQL comment syntax.
  
  read
  
  /*!40101 … */
  
  as
  
  ” this is a comment if the MySQL server is not version 4.1.1 or higher “
  
  That means that mysql versions lower than 4.1.1 will treat it as a comment, versions higher will execute what is inside.
  
  Also non-MySQL databases will treat it as a comment! It is used for 'pseudo-commenting' MySQL specific and version-specific syntax.
  
  The ” ! ” is commonly used in C-style programming languages meaning 'NOT'
  
  You can search the MySQL documentation for 'comments' …
- June 14, 2007 at 12:16 pm #24261
  
  maxhugen
  Participant
  
  Thanks for the explanation, Peter.
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