Example 1: Sorting German Umlauts
Suppose that column X
in table
T
has these latin1
column values:
Muffler Müller MX Systems MySQL
Suppose also that the column values are retrieved using the following statement:
SELECT X FROM T ORDER BY X COLLATE collation_name
;
The following table shows the resulting order of the values if
we use ORDER BY
with different collations.
latin1_swedish_ci |
latin1_german1_ci |
latin1_german2_ci |
Muffler | Muffler | Müller |
MX Systems | Müller | Muffler |
Müller | MX Systems | MX Systems |
MySQL | MySQL | MySQL |
The character that causes the different sort orders in this
example is the U with two dots over it
(ü
), which the Germans call
“U-umlaut.”
The first column shows the result of the
SELECT
using the
Swedish/Finnish collating rule, which says that U-umlaut
sorts with Y.
The second column shows the result of the
SELECT
using the German
DIN-1 rule, which says that U-umlaut sorts with U.
The third column shows the result of the
SELECT
using the German
DIN-2 rule, which says that U-umlaut sorts with UE.
Example 2: Searching for German Umlauts
Suppose that you have three tables that differ only by the character set and collation used:
mysql>CREATE TABLE german1 (
->c CHAR(10)
->) CHARACTER SET latin1 COLLATE latin1_german1_ci;
mysql>CREATE TABLE german2 (
->c CHAR(10)
->) CHARACTER SET latin1 COLLATE latin1_german2_ci;
mysql>CREATE TABLE germanutf8 (
->c CHAR(10)
->) CHARACTER SET utf8 COLLATE utf8_unicode_ci;
Each table contains two records:
mysql>INSERT INTO german1 VALUES ('Bar'), ('Bär');
mysql>INSERT INTO german2 VALUES ('Bar'), ('Bär');
mysql>INSERT INTO germanutf8 VALUES ('Bar'), ('Bär');
Two of the above collations have an A = Ä
equality, and one has no such equality
(latin1_german2_ci
). For that reason,
you'll get these results in comparisons:
mysql>SELECT * FROM german1 WHERE c = 'Bär';
+------+ | c | +------+ | Bar | | Bär | +------+ mysql>SELECT * FROM german2 WHERE c = 'Bär';
+------+ | c | +------+ | Bär | +------+ mysql>SELECT * FROM germanutf8 WHERE c = 'Bär';
+------+ | c | +------+ | Bar | | Bär | +------+
This is not a bug but rather a consequence of the sorting that
latin1_german1_ci
or
utf8_unicode_ci
do (the sorting shown is
done according to the German DIN 5007 standard).
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