We created our own hibernate type which is defined as a Type.Varbinary. In the pojo we define the column lenght (size = 16 ). In that same pojo the attribute is also used to create a unique index. Works fine with sqlserver, hsql and oracle 10G. In mysql 5.1 however, I get a nasty error | Reason: java.lang.RuntimeException: com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: BLOB/TEXT column 'PREFIX' used in key specification without a key length | The create statement: | create table MY_TEST_TABLE (id bigint not null, attr-3 tinyblob not null, attr-2 integer not null, attr-1 bigint not null, primary key (id), unique (attr-1, attr-2, attr-3(16))) | It seems like mysql wants you to set the size of the index fields for tiny (and probably any) blob fields, so it would look something like | create table MY_TEST_TABLE (id bigint not null, attr-3 tinyblob not null, attr-2 integer not null, attr-1 bigint not null, primary key (id), unique (attr-1, attr-2, attr-3)) We are using annotations, is there a way in hibernate to specify this? How have others handled this problem. TIA. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4018031#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...