A parameter is placeholder in a prepared statement where value of data is replaced at runtime (ie when the program is running).
It permits to reuse the same statement with different value. See SQL - Prepared Statement
A parameter can be:
Bind parameters cannot be used to define table, view or column names (the structure of an SQL statement should remain).
They are used in the where predicate parts
Example with the question mark ? ansi character used to mark the parameter
select columnName
from tableName
where
date_modified <= date(?,?,?,?) and
foo = ?
select *
from items
where item = ?;
select *
from items
where item = @it;
select *
from items
where item = :it ;
See also: