Mysql中常用双表批量更新、一对多查询

1、UPDATE 表1 a, 表2 b SET a.字段1 = b.字段1, a.字段2 = b.字段2 WHERE 条件1
例：

update income_invoice_profit_center a,income_invoice_collection o
        set a.profit_center_id = o.profit_center_id,a.profit_center_name=o.profit_center_name
        where a.invoice_code=o.invoice_code and a.invoice_num=o.invoice_num and
        a.profit_center_id is null

2、if(exp,值1，值2)

SELECT
		DISTINCT t1.id,
		t1.main_id,
		t1.name,
		if(t2.id is null,0,1) finish -- '1处理，0未处理'
		from tax_partner t1
		left join tax_declaration_report_partner t2
		on t1.id =t2.partner_id
		and t2.main_id=#{mainId} and t2.`month`=#{authMonth}

3、多表关联，一对多查询返回结果使用GROUP_CONCAT关键字，并GROUP BY

SELECT
		   a.id,
		   a.code,
	       GROUP_CONCAT(config.num) classification_list,
		   a.parent_name,
		   a.name,
		   a.tax_item,
		   a.simple_tax_rate,
		   a.commonly_tax_rate,
	       a.no_tax_method,
		   a.created_by,
		   a.created_date,
	       a.accounting_entries,
	   	   b.username as last_modified_by,
		   a.last_modified_date
	   FROM income_and_tax_rate_correspondence a
	   LEFT JOIN sys_user b on a.last_modified_by = b.id
	   LEFT JOIN subjects_classification_relation relation ON relation.subjects_id = a.id
	   LEFT JOIN sys_tax_classification_coding config ON relation.classification_id = config.id
	   
		   
			   a.code = #{code,jdbcType=VARCHAR}
		   
	   
	   GROUP BY a.id
	   order by a.last_modified_date desc
	   

4、Decode的使用
select t.*,d.name,DECODE(1,t.qy_bj,‘启用’,‘禁用’) qyZt
from a t
LEFT JOIN b d ON d.code = t2.ssyt