MySQL和PostgreSQL行子查询操作符

我在阅读MySQL文档时有点困惑 MySQL documentation

 A row subquery is a subquery variant that returns a single row and can thus return more than one column value. Legal operators for row subquery comparisons are:
  =  >  <  >=  <=  <>  !=  <=>

对于“=”文档提供了很好的解释:

SELECT * FROM t1 WHERE (column1,column2) = (1,1);
is same as:
SELECT * FROM t1 WHERE column1 = 1 AND column2 = 1;

create table example(a integer,b integer);
insert into example values (1,1);
insert into example values (1,2);
insert into example values (2,1);
select * from example where (a,b) > (1,1)
a | b
-----
1 | 2
2 | 1

游乐场: http://www.sqlfiddle.com/#!9/88641/2

附笔。:

• Oracle失败,错误为“ORA-01796:此运算符不能用于列表”