REPLACE [LOW_PRIORITY | DELAYED] [IGNORE] [INTO] tbl_name
{ [(col_name, ...)] VALUES (expression, ...), ...
| [(col_name, ...)] SELECT ...
| SET col_name=expression, col_name=expression, ... }
REPLACE is identical to INSERT, except that if an inserted row clashes with an existing row in a PRIMARY KEY or UNIQUE column, the old entry is replaced with the new.