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Replication of Columns Having Different Data Types

Corresponding columns on the master's and the slave’s copies of the same table ideally should have

the same data type. However, beginning with MySQL 5.1.21, this is not always

strictly enforced, as

long as certain conditions are met.

Ali other things being equal, it is always possible to replicate from a column of a given data type to

another column of the same type and same size or width, where applicable, or larger. For example,

you can replicate from a CHAR (10) column to another CHAR (10), or from a CHAR (10) column to a

CHAR (25) column without any problems. In certain cases, it also possible to replicate from a column

having one data type (on the master) to a column having a different data type (on the slave); when the

data type of the master’s version of the column is promoted to a type that is the same size or larger on

the slave, this is known as ałtribute promotion.

Attribute promotion can be used with both statement-based and row-based replication, and is not

dependent on the storage engine used by either the master or the slave. However, the choice of

logging format does have an effect on the type conversions that are permitted; the particulars are

discussed later in this section.