Hello,

When defining a field as unique within a table, I understand that you use Unique(fieldname) when creating the table.

I'm using a BLOB to store a long string, and want these long strings to be unique. If I try to use Unique(type) (where type is a blob) I get the error:

Error 1170 Blob column 'type' used in key specification without a key length

Does anybody know how I can make ths Blob unique?

Cheerz,

Steve

I'm sorry, i'm a little confused!

How do I use the code:
CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));

to make blob_col unique?

i am confused about your confusion

since your table exists already, there's little point in using CREATE TABLE

you will probably want to try this --

ALTER TABLE yourtable
ADD UNIQUE(blob_col(10)));

I am building the database at the moment fo a university project so am just dropping and recreating the whole database as it changes - that is why I am using create table.

I am currently creating the table as:

CREATE TABLE TOOL (toolNumber INT NOT NULL AUTO_INCREMENT, type BLOB, location VARCHAR(255), returnDate VARCHAR(30), PRIMARY KEY(toolNumber));

Now I want to change this so that the field type is unique.

The statments

CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));

ALTER TABLE test
ADD UNIQUE(blob_col(10));

return the error:
ERROR 1061: Duplicate key name 'blob_col'

that should not really surprise you

you create an INDEX on the blob column, then attempt to add a UNIQUE index as well

may i suggest you define only one index on the column