MySQL检查是否存在多行 [英] MySQL check if multiple rows exist

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本文介绍了MySQL检查是否存在多行的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

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

如何有效地存在表中的多行，如:

How to efficiently existance of multiple rows from table like:

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

仅在找到两行(键0和2)时才返回正值?

to return positive only if both rows (with key 0 and 2) was found?

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

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