="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>     <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> versions before 9.0 would try
     to substitute the variable in all three cases, leading to syntax errors.
    </P
></BLOCKQUOTE
></DIV
><P
>    Since the names of variables are syntactically no different from the names
    of table columns, there can be ambiguity in statements that also refer to
    tables: is a given name meant to refer to a table column, or a variable?
    Let's change the previous e