Replication Features and Issues •Columns common to both versions of the table must be defined in the same order on the source and the replica. (This is true even if both tables have the same number of columns.) •Columns common to both versions of the table must be defined before any additional columns. •Each “extra”  column in the version of the table having more columns must have a default value. 3658 source>  CREATE TABLE t1 (c3 INT, c1 INT, c2 INT); replica> CREATE TABLE t1 (c1 INT, c2 INT); source>  CREATE TABLE t1 (c1 INT, c2 INT, c3 INT); replica> CREATE TABLE t1 (c2 INT, c1 INT); source>  CREATE TABLE t1 (c1 INT, c2 INT, c3 INT); replica> CREATE TABLE t1 (c1 INT, c2 INT); CREATE TABLE t ( c1 INT, c2 INT, c3 INT ); ALTER TABLE t ADD COLUMN cnew1 INT AFTER c3; This means that executing an  ALTER TABLE  statement on the replica where a new column is inserted into the table within the range of columns common to both tables causes replication to fail, as shown in the following example: Suppose that a table  t , existing on the source and the replica, is defined by the following  CREATE TABLE  statement: Suppose that the  ALTER TABLE  statement shown here is executed on the replica: The previous  ALTER TABLE  is permitted on the replica because the columns  c1 ,  c2 , and  c3  that are common to both versions of table  t  remain grouped together in both versions of the table, before any columns that differ. However, the following  ALTER TABLE  statement cannot be executed on the replica without causing replication to break: ALTER TABLE t ADD COLUMN cnew2 INT AFTER c2; Replication fails after execution on the replica of the  ALTER TABLE  statement just shown, because the new column  cnew2  comes between columns common to both versions of  t . A column’s default value is determined by a number of factors, including its type, whether it is defined with a  DEFAULT  option, whether it is declared as  NULL , and the server SQL mode in effect at the time of its creation; for more information, see Section 11.6, “Data Type Default Values” ). In addition, when the replica’s copy of the table has more columns than the source’s copy, each column common to the tables must use the same data type in both tables. Examples.   The following examples illustrate some valid and invalid table definitions: More columns on the source.   The following table definitions are valid and replicate correctly: The following table definitions would raise an error because the definitions of the columns common to both versions of the table are in a different order on the replica than they are on the source: The following table definitions would also raise an error because the definition of the extra column on the source appears before the definitions of the columns common to both versions of the table: