REPLACE Statement REPLACE  works exactly like  INSERT , except that if an old row in the table has the same value as a new row for a  PRIMARY KEY  or a  UNIQUE  index, the old row is deleted before the new row is inserted. See Section 13.2.6, “INSERT Statement” . REPLACE  is a MySQL extension to the SQL standard. It either inserts, or  deletes  and inserts. For another MySQL extension to standard SQL—that either inserts or  updates —see Section 13.2.6.2, “INSERT ... ON DUPLICATE KEY UPDATE Statement” . DELAYED  inserts and replaces were deprecated in MySQL 5.6. In MySQL 8.0,  DELAYED  is not supported. The server recognizes but ignores the  DELAYED  keyword, handles the replace as a nondelayed replace, and generates an  ER_WARN_LEGACY_SYNTAX_CONVERTED  warning:  REPLACE DELAYED is no longer supported. The statement was converted to REPLACE . The  DELAYED  keyword is scheduled for removal in a future release. release. REPLACE  makes sense only if a table has a  PRIMARY KEY  or  UNIQUE  index. Otherwise, it becomes equivalent to  INSERT , because there is no index to be used to determine whether a new row duplicates another. Values for all columns are taken from the values specified in the  REPLACE  statement. Any missing columns are set to their default values, just as happens for  INSERT . You cannot refer to values from the current row and use them in the new row. If you use an assignment such as  SET  col_name  =  col_name  + 1 , the reference to the column name on the right hand side is treated as  DEFAULT( col_name ) , so the assignment is equivalent to  SET  col_name  = DEFAULT( col_name ) + 1 . In MySQL 8.0.19 and later, you can specify the column values that  REPLACE  attempts to insert using VALUES ROW() . To use  REPLACE , you must have both the  INSERT  and  DELETE  privileges for the table. If a generated column is replaced explicitly, the only permitted value is  DEFAULT . For information about generated columns, see Section 13.1.20.8, “CREATE TABLE and Generated Columns” . REPLACE  supports explicit partition selection using the  PARTITION  clause with a list of comma-separated names of partitions, subpartitions, or both. As with  INSERT , if it is not possible to insert the new row into any of these partitions or subpartitions, the  REPLACE  statement fails with the error  Found a row not matching the given partition set . For more information and examples, see Section 24.5, “Partition Selection” . The  REPLACE  statement returns a count to indicate the number of rows affected. This is the sum of the rows deleted and inserted. If the count is 1 for a single-row  REPLACE , a row was inserted and no rows were deleted. If the count is greater than 1, one or more old rows were deleted before the new row was inserted. It is possible for a single row to replace more than one old row if the table contains multiple unique indexes and the new row duplicates values for different old rows in different unique indexes. The affected-rows count makes it easy to determine whether  REPLACE  only added a row or whether it also replaced any rows: Check whether the count is 1 (added) or greater (replaced). If you are using the C API, the affected-rows count can be obtained using the  mysql_affected_rows() function. You cannot replace into a table and select from the same table in a subquery. 2659 assignment_list : assignment  [,  assignment ] ... Note