MySQL检查是否存在多行

Question

Here you can find how to check row existance:
SELECT EXISTS(SELECT 1 FROM table1 WHERE some_condition);

如何从表中有效地存在多行:

SELECT EXISTS(SELECT 1 FROM table1 WHERE key = 0);
SELECT EXISTS(SELECT 1 FROM table1 WHERE key = 2);

来自表格:

key,username
0,foo
1,bar
2,boo

仅当找到两行(具有键 0 和 2)时才返回正数？

Answer 1

SELECT count(distinct key) = 2  FROM table1 WHERE key in (0, 2)