@param columnName
@param tableAlias
@param pattern if pattern is null,it will be set {%Y-%m-%d %H:%i:%s} as mysql default value and set {yyyy-mm-dd
hh24:mi:ss} as oracle default value
@param dbType {@link DBType} if dbType is null ,it will be set the mysql as a default value
@param columnName @param tableAlias @param pattern if pattern is null,it will be set {%Y-%m-%d %H:%i:%s} as mysql default value and set {yyyy-mm-dd hh24:mi:ss} as oracle default value @param dbType {@link DBType} if dbType is null ,it will be set the mysql as a default value