mysql自定义函数返回表对象

MySQL自定义函数可以返回表对象，但需要使用游标和存储过程来实现。

下面是一个示例代码，该代码定义了一个自定义函数，该函数返回一个包含所有顾客信息的表对象。

DELIMITER //
CREATE FUNCTION get_customers()
RETURNS TABLE
BEGIN
    DECLARE cursor1 CURSOR FOR SELECT * FROM customers;
    DECLARE continue_handler BOOLEAN DEFAULT TRUE;
    DECLARE customer_id INT;
    DECLARE customer_name VARCHAR(255);
    DECLARE customer_email VARCHAR(255);
    DECLARE customer_phone VARCHAR(255);
    DECLARE customer_address VARCHAR(255);
    DECLARE customer_table TABLE(customer_id INT, customer_name VARCHAR(255), customer_email VARCHAR(255), customer_phone VARCHAR(255), customer_address VARCHAR(255));
    
    DECLARE EXIT HANDLER FOR NOT FOUND SET continue_handler = FALSE;

    OPEN cursor1;

    read_loop: LOOP
        FETCH cursor1 INTO customer_id, customer_name, customer_email, customer_phone, customer_address;
        IF NOT continue_handler THEN
            CLOSE cursor1;
            LEAVE read_loop;
        END IF;
        INSERT INTO customer_table VALUES (customer_id, customer_name, customer_email, customer_phone, customer_address);
    END LOOP;

    RETURN SELECT * FROM customer_table;
END//
DELIMITER ;

该函数使用游标从顾客表中检索数据，并将数据插入到一个临时表对象中。最后，该函数返回临时表对象。

可以使用以下命令调用此函数：

SELECT * FROM get_customers();

这将返回包含所有顾客信息的表对象。