mysql嵌套查询如何优化

CREATE INDEX idx_column_name ON table_name(column_name);

SELECT *
FROM table1
JOIN table2 ON table1.id = table2.id
WHERE table2.column = 'value';

CREATE TEMPORARY TABLE temp_table AS
SELECT column1, column2
FROM table1
WHERE condition;

SELECT *
FROM temp_table
JOIN table2 ON temp_table.id = table2.id;

EXPLAIN SELECT * FROM table1 WHERE column IN (SELECT column FROM table2);

SELECT customer_name, (
    SELECT COUNT(*)
    FROM orders
    WHERE orders.customer_id = customers.id
) AS order_count
FROM customers;

SELECT customers.customer_name, COUNT(orders.id) AS order_count
FROM customers
LEFT JOIN orders ON customers.id = orders.customer_id
GROUP BY customers.id;