Question

I created a table and set the collation to utf8 in order to be able to add a unique index to a field. Now I need to do case insensitive searches, but when I performed some queries with the collate keyword and I got:

mysql> select * from page where pageTitle="Something" Collate utf8_general_ci;

ERROR 1253 (42000): COLLATION ‘utf8_general_ci’ is not valid for
CHARACTER SET ‘latin1’

mysql> select * from page where pageTitle="Something" Collate latin1_general_ci;

ERROR 1267 (HY000): Illegal mix of collations (utf8_bin,IMPLICIT) and
(latin1_general_ci,EXPLICIT) for operation ‘=’

I am pretty new to SQL, so I was wondering if anyone could help.

Answer 1

A string in MySQL has a character set and a collation. Utf8 is the character set, and utf8_bin is one of its collations. To compare your string literal to an utf8 column, convert it to utf8 by prefixing it with the _charset notation:

_utf8 'Something'

Now a collation is only valid for some character sets. The case-sensitive collation for utf8 appears to be utf8_bin, which you can specify like:

_utf8 'Something' collate utf8_bin

With these conversions, the query should work:

select * from page where pageTitle = _utf8 'Something' collate utf8_bin

The _charset prefix works with string literals. To change the character set of a field, there is CONVERT … USING. This is useful when you’d like to convert the pageTitle field to another character set, as in:

select * from page 
where convert(pageTitle using latin1) collate latin1_general_cs = 'Something'

To see the character and collation for a column named ‘col’ in a table called ‘TAB’, try:

select distinct collation(col), charset(col) from TAB

A list of all character sets and collations can be found with:

show character set
show collation

And all valid collations for utf8 can be found with:

show collation where charset = 'utf8'