oracle - Regarding sql script -

I have the following line in a .sql script. Not sure what it does, does it wait for user to input for password and password, or does it take value from the environment? & amp; Amp; What does it denote? Before creating the saee table below the line in the test.sql file:

  connect & amp; & Amp; Usr / & amp; & Amp; Passed @ & amp; & Amp; Dbname  

In this SQL script you specify usr, pass and dbname in the form of novel variables Are declaring. From:

Both single ampersands (& amp;) and twice ampersands ( Plus changes the value of the pre-processing statement and the variable.The statement is executed. If the variable was not defined before SQL, then plus indicates a value before substitution. / P>

A single ampersand prefix is ​​used with an undefined variable, then the value you want The entry on the ramp is not stored after the statement, the value is abandoned immediately after the value is replaced and the variable is unclassified mandatory. If the variable is referred to twice, even in the same command, you can Two values ​​indicate that different values ​​can be entered at each prompt.

If a double ampersand reference gives you a value for the SQL plus a value, then The PL plus variable defines that value. Any subsequent reference (even in the same command) of the variable either "& amp; or" & amp; amp; "New defined value Replaces SQL * Plus will not prompt you again.

And here it is.