SQL unique varchar case sensitivity question

Question

I'm trying to populate a SQL table with a list of words. The table itself it pretty simple:

CREATE TABLE WORDS(
  ID BIGINT AUTO_INCREMENT, 
  WORD VARCHAR(128) NOT NULL UNIQUE, 
  PRIMARY KEY(ID)
);

The problem I'm running into is this: when I do the following inserts back to back

INSERT INTO WORDS(WORD) VALUES('Seth');
INSERT INTO WORDS(WORD) VALUES('seth');

The second insert fails with a constraint violation ("Duplicate entry 'seth' for key 'WORD'").

How can I get the UNIQUE constraint on WORD to be case sensitive?

Solution 1

Looks like mysql is case insensitive by default:

You probably need to create the column with a case sensitive collation (e.g. utf8_bin):

CREATE TABLE WORDS (
    ID BIGINT AUTO_INCREMENT, 
    WORD VARCHAR(128) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL UNIQUE, 
    PRIMARY KEY(ID)
);

Solution 2

By default MySQL ignores differences in case and trailing spaces on varchar.

If you need it to be case sensitive, you can alter the table to be varchar(...) binary.

Use show create table to better understand how MySQL converts this to full notation.

If you need to pay attention to trailing spaces as well as be case sensitive, use varbinary instead of varchar.

Solution 3

Try this:

ALTER TABLE WORDS CONVERT TO CHARACTER SET utf8 COLLATE utf8_bin;

Comments

[Seth]

That did it. Thanks. For anyone finding this question later, I had to use the 'utf8_bin' collation because mysql didn't have 'utf8_cs'.

[groovenectar]

Thanks @Seth, that was helpful along with Bill's info, utf8_bin applied to my situation as well

[feedc0de]

#1273 - Unknown collation: 'utf8_cs'

[Josef Sábl]

Huge disappointment with mysql :-( "Seth" and "seth" are NOT same strings! Thanks for helping out.

[Lauris Kuznecovs]

Use utf8_bin in case of utf8_cs

[stamster]

I have collation set as utf8_bin. And still varchar(50) FFAB213D-810C-74BD-1B34-E93FC473CF6A is the same as ffab213D-810C-74BD-1B34-E93FC473CF6A (MariaDB 10)

[Xhua]

For utf8mb4, you can use SET utf8mb4 COLLATE utf8mb4_bin instead.

[Surajit Biswas]

Many Thanks man, my clients were about to file case on me. Use this jol.ink