mysql - 优化 MySQL 的重复查询

Question

我有以下查询来检查表的两列是否在另一个中 查询有效，我希望您可以优化调用，因为它们是相等的。我怀疑是否会因为对同一查询进行两次调用而导致性能损失

SELECT name,lastname FROM TABLA_A
WHERE 
name IN (
  SELECT name FROM TABLE_B
)
OR
lastname IN (
  SELECT lastname FROM TABLE_B
)

另一种方式

SELECT a.name,a.lastname
FROM TABLE_A as a
join TABLE_B  as b on a.name=b.name
or a.lastname= b.lastname

try to join, is a valid option? there are other ways to make this task more efficient? thank you very much

Answer 1

使用 OR 存在性能问题，您可以使用 UNION 代替，如下所示:

SELECT name, lastname 
FROM TABLE_A
WHERE name IN (
  SELECT name 
  FROM TABLE_B)
UNION -- If there is not any duplicate use `UNION ALL` instead
SELECT name, lastname 
FROM TABLE_A
WHERE lastname IN (
  SELECT lastname 
  FROM TABLE_B);

[SQL Fiddle Demo]