MySQL技巧

类型转换

SELECT CONVERT(`merchant_id`, CHAR) FROM `merchant_info`

对查询为null的值赋默认值

select ifnull(字段,0) from 表名

SELECT ifnull(SUM(r.refunded_amount), 0) as refunded_amount
    FROM refund_order r
    WHERE r.pay_order_no = p.pay_order_no

显示binlog变量

SHOW VARIABLES like "%binlog%"

字段内容替换

update merchant_document d set d.doc_path = REPLACE(d.doc_path, 'prod/appblog', 'appblog/prod')