ont color="black"><b>constraint:</b></font></dt><dd><font color="black"> 
When we tell the database to enforce a rule on a field or a row
in a table. A common constraint is to insist that there can be no
duplicate values in a particular field (i.e. all the values must be unique).
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<br />
</dd><dt><font color="black"><b>cursor:</b></font></dt><dd><font color="black"> A cursor allows you to execute SQL commands in a database
and retrieve data from the database. A cursor 