Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation '=

问题描述：MySQL进行字符串比较时发生错误：

SELECTa.equ_no,b.fullCodeFROMequipment a,(SELECTt.*, getEquTypeFullCode (t.equType_id) AS fullCodeFROMequ_type t) bWHEREsubstring(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”

SELECTa.equ_no,b.fullCodeFROMequipment a,(SELECTt.*, getEquTypeFullCode (t.equType_id) AS fullCodeFROMequ_type t) bWHEREsubstring(a.equ_no, 1, 5) = CONVERT(b.fullCode USING utf8) COLLATE utf8_unicode_ci;