官网给的demo

exists(String existsSql)
exists(boolean condition, String existsSql)
 

exists("select id from table where age = 1")--->exists (select id from table where age = 1)

新版本mybatis-plus 有三个参数

Children exists(String existsSql, Object... values);

Children exists(boolean condition, String existsSql, Object... values);

用法要有改变，原来那么用也可以，但是不严谨

exists("select 1 from TABLE where id = {0} and name = {1}", "123", "456");