x001: mysql多表的select、delete、update、Insert

多表删除 table

delete a,b from a_table a LEFT JOIN b_table b on a.a_id=b.b_id;select

多表更新 统计

UPDATE a_table a,b_table b SET b.b_part="12dd13",a.a_name="老刘1ds" where a.a_id=b.b_id and b.b_id=5查询

分组查询并统计次数大于0tab

select b.b_name,count(*) as count from b_table b GROUP BY b.b_name HAVING count>0;vi

用having就必定要和group by连用,
用group by不一有having (它只是一个筛选条件用的)
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