SQL - Parameter (Bind | Substitution) (Marker | Variable)

About

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).

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 ;