不常用但偶爾用的SQL，不定時更新

1.update left join 多表關聯更新

UPDATE table_1 t1 left join table_2 t2 on t2.id = t1.tid SET 需要修改的字段信息
where 條件;

2.select count(字段名) group by 分組查詢數量大於1的

SELECT COUNT(name) FROM table GROUP BY name HAVING COUNT(name) >1;