如何通过多个 JOIN 提高 SQL 查询的性能？

Question

我有一个 SQL 查询，涉及多个表之间的多个 JOIN，并且执行速度非常慢。这是我的查询的简化版本：

SELECT 
    a.column1,
    b.column2,
    c.column3
FROM 
    table1 a
JOIN 
    table2 b ON a.id = b.a_id
JOIN 
    table3 c ON b.id = c.b_id
WHERE 
    a.column4 = 'some_value';

The tables have the following characteristics:

table1 has around 500,000 rows.

table2 has around 1,000,000 rows.

table3 has around 200,000 rows.

Indexes are present on the id columns of each table. What are some strategies I can use to optimize this for better performance? Any advice on rewriting, indexing, or other optimizations would be greatly appreciated.

Expecting:
Strategies to optimize this query for better performance.

Advice on query rewriting, indexing techniques, or other optimizations.

Answer 1

您提到您在每个表的 id 上都有索引，但是在您的示例中，您在外键（a_id，b_id）上有索引吗？ 如果是普通搜索，您在查询中使用的列是否有索引？