Controlling Case Sensitivity of String Sorts
Problem
String sorts are case sensitive when you don’t want them to be, or vice versa.
Solution
Alter the case sensitivity of the sorted values.
Discussion
Chapter 4 discusses the fact that binary strings
are case sensitive in comparisons, whereas non-binary strings are
not. This property carries over into string sorting as well:
ORDER
BY
produces
lexical sorts that are case sensitive for binary strings and not case
sensitive for non-binary strings. The following table
textblob_val
contains a TEXT
column tstr
and a BLOB
column
bstr
that serve to demonstrate this:
mysql> SELECT * FROM textblob_val;
+------+------+
| tstr | bstr |
+------+------+
| aaa | aaa |
| AAA | AAA |
| bbb | bbb |
| BBB | BBB |
+------+------+
Both columns contain the same values. But they produce different sort
results, because TEXT
columns are not case
sensitive and BLOB
columns are:
mysql>SELECT tstr FROM textblob_val ORDER BY tstr;
+------+ | tstr | +------+ | aaa | | AAA | | bbb | | BBB | +------+ mysql>SELECT bstr FROM textblob_val ORDER BY bstr;
+------+ | bstr | +------+ | AAA | | BBB | | aaa | | bbb | +------+
To control case sensitivity in ORDER
BY
clauses, use the techniques discussed in Chapter 4 for affecting string comparisons. To perform a
case-sensitive sort for strings that are not case sensitive (such as
those in the tstr
column) cast the sort column to
binary-string form using the
BINARY
keyword:
mysql> SELECT tstr FROM textblob_val ORDER BY BINARY ...
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