查询如下以设置用户定义的会话变量 -
mysql> set @sentence='thks ks is a my string';query ok, 0 rows affected (0.00 sec)
在此，k 只会被 i 替换一次。查询如下。我们也使用了 instr() -
mysql> select @sentence as newstring ,concat(replace(left(@sentence,instr(@sentence, 'k')), 'k', 'i'), -> substring(@sentence, instr(@sentence, 'k') + 1)) as changeonlyonetime;
以下是仅显示第一次出现的字符被替换的输出 -
+------------------------+------------------------+| newstring | changeonlyonetime |+------------------------+------------------------+| thks ks is a my string | this ks is a my string |+------------------------+------------------------+1 row in set (0.00 sec)
以上就是仅对 mysql 中会话变量第一次出现的字符执行搜索/替换的详细内容。