mysql 'OR'，'IN'，‘union’效率分析

1、
EXPLAIN (SELECT * FROM m_news WHERE TYPES = 5 )
UNION  (SELECT * FROM m_news WHERE TYPES = 10 );

2、
EXPLAIN SELECT * FROM m_news WHERE TYPES = 5 OR TYPES =10;

3、
EXPLAIN SELECT * FROM m_news WHERE TYPES IN (5,10);

结论：从影响行数来说，用'or'和‘in’ 效果是一样的，‘union’效率高很多。