Create return create sql with the provided tbname and columns.

Drop return the drop sql with the provided tbname and columns.

Refresh first Reset, then Upgrade.

Register register the Migration in the map.

Reset reset all migration run all migration's down function.

Rollback rollback the migration by the name.

TableDDL is still in think.

Upgrade upgrate the migration from lasttime.

const the data format for the bee generate migration datatype.

const the data format for the bee generate migration datatype.

Column define the columns name type and Default.

Migration the basic type which will implement the basic type.

Table store the tablename and Column.

Migrationer is an interface for all Migration struct.