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    <p><strong>- Answer to problem 1:</strong> The first type of variables is called Substitution Variables which only works in SQL*Plus and SQL Developer. So when you supply a substituation vaiable in any SQL statement, SQL*Plus replaces the variable with it's value. It has nothing to do with Oracle server or performance. The example you gave will be translated to the follwing BEFORE sending it to the Oracle database server:</p> <pre><code>select * from customer where name = 'Joe'; </code></pre> <p>The second part is called bind variables which is not exclusive to SQL*Plus or SQL Developer as you can use it, for example, in a Java application (or other languages) connecting to Oracle. Bind variables provide better performance when you run the same statement many times as you always submit the statement as it is (without rewriting). Then the variables get evaluated at the database level. For example, let's say you've changed the value of "first_name" to "Mark":</p> <pre><code>exec :first_name:= 'Mark'; </code></pre> <p>The same statement with the bind variable is submitted to Oracle database server. The database uses cached area to find that the same statement was run perviously and uses it again. Then the database uses the variables values. This means the database will not need to re-parse and re-calculate the best execution plan for the same statement. But this is not the case with the first type(Substitution Variables).</p> <p><strong>- Answer to problem 2:</strong> No you can't, because as I said above, all what SQL*Plus or SQL Developer do is just rewriting the statement replacing the variable name with it's value. It doesn't know anything about it's type. Only text replacement is done here.</p> <p>You can find more details here: <a href="http://www.oracle-base.com/articles/misc/literals-substitution-variables-and-bind-variables.php" rel="nofollow">http://www.oracle-base.com/articles/misc/literals-substitution-variables-and-bind-variables.php</a></p>
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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