Know About >> MySQL


  • MyISAM does not support the foreign key constraint and transaction but InnoDB supports it.
  • MyISAM is faster then the InnoDB but in case of perforing the count operation it takes more time then the InnoDB.
  • MyISAM occupies less memory sapce for tables rather than InnoDB tables.

Different types of keys in Database

  • Primary key-unique, not null-uniquely identify a each row of the table.
  • Super key-if we add some additional attributes to primary key then the resultant combination would still be uniquely identify an instance of the entity set. A PK key is therefore a minimum superkey.
  • Foreign key-PK of another table.
  • Candidate key-nominee’s for primary key(it has all the characteristics to be a PM but it’s not the PK)
  • Alternate key-a candidate key which is not PK is called alternate key.
  • Composite key-more than one primary key jointly known as composite key.

MySQL default character set: latin1
Default collation for latin1 is ‘latin1_swedish_ci’

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