Using CURRENT, DATETIME, INTERVAL, and NULL in INSERT

A UDR cannot insert a variable that was declared using the CURRENT, DATETIME, INTERVAL, or NULL keywords as the name. For example, if you declare a variable called null, when you try to insert the value null into a column, you receive a syntax error, as the following example shows:

CREATE PROCEDURE problem()
. . .
DEFINE null INT;
LET null = 3;
INSERT INTO tab VALUES (null); -- error, inserts NULL, not 3