问题描述：MySQL进行字符串比较时发生错误：
-
SELECT -
a.equ_no, -
b.fullCode -
FROM -
equipment a, -
( -
SELECT -
t.*, getEquTypeFullCode (t.equType_id) AS fullCode -
FROM -
equ_type t -
) b -
WHERE -
substring(a.equ_no, 1, 5) = b.fullCode
错误如下：
[Err] 1267 - Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '='
解决方法：将比较等式一边进行字符串转换，如改为“CONVERT(b.fullCode USING utf8) COLLATE utf8_unicode_ci”
-
SELECT -
a.equ_no, -
b.fullCode -
FROM -
equipment a, -
( -
SELECT -
t.*, getEquTypeFullCode (t.equType_id) AS fullCode -
FROM -
equ_type t -
) b -
WHERE -
substring(a.equ_no, 1, 5) = CONVERT(b.fullCode USING utf8) COLLATE utf8_unicode_ci;